I've been thinking on this ever since the changes were announced. It's very easy to think about how disappointing this change is as a Ninja player -- our job goes from being the rDPS job it has always been to being a selfish job with a bog-standard two-minute buff that's somehow better and worse than most other two minute buffs in the game.
However, Ninja is far from the only class that's impacted by Trick Attack. Removing the last remaining 1-minute buff has dire implications for skill expression across the board. Do you have excess gauge to spend between two-minute buffs? Doesn't matter where you spend it. Have extra stacks of a skill to use up before you overcap? It doesn't matter anymore if you use it now or in twenty second's time. You can turn your brain off outside of those crucial two-minute windows.
To me, this is heart-breaking, as I was really hoping the game would move in favour of more buffs on odd -- or at least 1-minute -- timers. Two minute timers mean you only really get three -- maybe four in early weeks -- burst windows per fight. That's not a lot.
The reason for the changes to Trick Attack were to 'increase synergy with other classes'. I fully believe that the changes do not serve the stated purpose, and in fact decrease the synergy Ninja has with other classes.
The first point of note is that Ninja already synergised well with two-minute buff windows, by virtue of Trick Attack being on a one-minute timer. Changing the party buff to Mug on a two-minute timer does not increase synergy with other classes, as this synergy already existed!
I'm not an expert on other classes, and I invite other players with more experience to come and offer their thoughts on what each class's 'synergy' is with the one-minute party buff that used to be Trick Attack. That said, I'd like to briefly outline what each class could potentially bring to a Trick Attack window, to the best of my understanding. I will update this post if other players correct me or suggest other abilities.
Melee DPS
Samurai
Samurai is able to pool Kenki and unleash several Shintens within the one-minute buff window, as opposed to mindlessly spending them at any point between two-minute windows. Higanbana, the SAM DOT, also lasts sixty-seconds, meaning that a Samurai would be able to maintain full buff uptime on their DOT, by alternating refreshing it during one and two minute windows.
Monk
Monk already has a personal buff, Riddle of Fire, which aligns perfectly with Trick Attack. I'm unsure if anything in particular would change in the Monk rotation, but given that it naturally aligns, I can't imagine much would change. Monk would also benefit from refreshing its DOT under Trick.
Dragoon
Dragoon also has a personal buff - Lance Charge - on a 60s cooldown, and additionally has Spineshatter Dive, Geirskogul, Stardiver, High Jump, Mirage Dive -- an absolute swathe of abilities to pour into Trick Attack. Like the other melees, Dragoon also benefits from refreshing its DOT under Trick.
Reaper
While I have the weakest understanding of this job of the melees, I understand it is able to pour an Enshroud window into Trick, which is a substantial amount of burst, as it generates ~3 Enshroud windows every two minutes. Two Enshrouds will go into 2-minute buffs, and one is left over. Reaper, unlike the melees, however, does not have a DOT, but similar to Samurai loses out the most by no longer having a meaningful place to expend the extra Enshroud window.
Caster DPS
Summoner
Summoner should naturally align with Trick Attack, with the Demi-phases of their rotation coming in every sixty seconds. As I understand it, Summoners would prioritise going into Titan-phase immediately after their Demi with a Ninja in the party, to maximise the value of Trick Attack. Additionally, getting Enkindle under Trick Attack is a small optimisation that can benefit the party.
Red Mage
As I understand it, Red Mage is almost always able to dump a melee combo into Trick Attack, as they naturally overcap enough for a single melee combo, much like with Reaper's Enshroud. Without Trick Attack, it doesn't matter where Red Mage dumps this additional combo.
Black Mage
As I understand it, Black Mage generally ignores raid buffs to prioritise maximising its sustained damage, but depending on the fight Black Mage might be able to pour Xenoglossies into Trick Attack, allowing for a small optimisation of optimisation.
Ranged Physical DPS
Bard
Bard, being a heavily proc-based class, does not have a large number of abilities to play into Trick, but should be able to fit an Empyrean Arrow and Apex Arrow -> Blast Arrow into every Trick Window.
Machinist
Machinist would always have the Automaton Queen available, as well as Reassemble charge, Chain Saw, and a Hypercharge window available to pour into Trick Attack.
Dancer
Dancer should be able to fit a Standard Step and Flourish under Trick Attack, as well as pooling any excess feathers gained from GCDs, which is a substantial amount of burst.
Tanks
Paladin
Paladins have a personal damage buff -- Fight or Flight -- which naturally aligns with Trick Attack's party buff. They'd also be able to reapply the DOT from Goring Blade under Trick. As I understand it, however, Paladin doesn't align naturally with Trick, and often uses its most potent abilities outside of one-minute windows for rotational reasons.
Warrior
Warrior's Inner Release window now aligns perfectly with Trick Attack's timer, allowing them to get a huge amount of burst out during one-minute intervals.
Dark Knight
Blood Weapon and Delirium are each on a sixty-second cooldown, allowing DRK to build massive amounts of MP and expend a large number of Flood of Shadows each minute. In addition, Carve and Spit can be poured into Trick, too.
Gunbreaker
GNB has a personal buff, similar to Paladin -- No Mercy -- on a 60s cooldown, which aligns naturally with Trick. It can pour a lot of abilities into Trick, too -- Danger Zone, Sonic Break (which also applies a DOT), Rough Divide (x2), the Gnashing Fang combo, Bow Shock, Blasting Zone, Double Down -- the list goes on. It's no surprise to say that Gunbreaker synergises particularly strongly with Trick Attack's one-minute raid buff.
Healers
(yes, even healers)
White Mage
With Lillies now being on a 20s charge instead of a 30s charge, WHM is able to generate one Afflatus Misery per minute. Pouring this into Trick would be a huge gain. In addition, Assize will align with every third Trick Attack, for a small gain in potency. Naturally, Dia can also be refreshed in Trick for a gain in potency.
Scholar
Aetherflow is a 60s cooldown, which while normally used to fuel Lustrate and Sacred Soil, can being used to dump damage with Energy Drain. These dumps can be poured into Trick for a small potency gain. Similar to WHM, SCH can also refresh Biolysis in Trick for a gain in potency.
Astrologian
Astrologian, similar to other healers, enjoys the boost to Combust II from refreshing it during Trick Attack. Earthly Star also lines up perfectly with Trick, on a 60s cooldown.
Sage
Phlegma III stacks can be pooled and dumped during Trick Windows. Similar to the other healers, it can also refresh Eukrasian Dosis II under Trick for a small gain in potency.
Once again, I do not believe all (or even any) of these are entirely correct statements. I could be completely wrong about a job's ability to play into Trick, and I encourage you to correct me or offer your own contributions where I've failed to.
However, I hope this post demonstrates just how much synergy between each job and Trick Attack already existed. All of this is lost to us as of 6.1.
I would ask the developers to elaborate on where, exactly, the synergy from Mug exists where it did not with Trick Attack, and why they believe it has increased. As it stands, I do not believe that their stated reasoning for the changes to Trick Attack lines up with the actions taken.