It's a bit of a mixed bag for me, but I accept the idea of what they're trying to do. On one hand, I actually like ninjas having more personal damage on their burst. If their personal burst felt weak, then they just feel like a gimped "burst" job tied to Trick Attack in content outside of raiding because the RDPS gain locks them into a design for only being a Trick Attack buffer and lacking any job fantasy outside of support. In a way, opening the design for Trick Attack to be a personal buff allows more flexibility in design as you can only fit in so many skill changes in a 15 second burst window before everything crumbles apart by next expansion with the introduction of a new skill or two. We can already see that happening with the removal of Shadowfang and replacing it with Phantom Kamaitachi, but for ninjas where their damage is their initial burst window, it's even more damaging on the leveling process.
At the same time, because the game is designed under 60 second burst windows (WAR getting the 60 second timer on IR for example), mug feels VERY out of place now - because Ninja's second identity is raidwide damage burst buff every 60 seconds. Changing party buff to a 120 second window makes the window very inflexible in its own way.
Essentially, Ninja's been suffering from its 2 unique identities - job fantasy wise (a high initial personal burst damage job for its assassin-like gameplay + a support burst job with Trick Attack). Because the higher level you go % buffs actually increase significantly as more jobs get more skills + stats, the personal burst & future skill potencies for ninja had to be lowered to compensate. The developers had this problem with Trick Attack in the past (10% party buff but shorter buff duration) where ninja is usually left in this weird state of balancing which led Ninja to feel really weak or really strong in terms of its personal damage to its overall damage. Ninja would be 'overpowered' / acceptable with trick attack padding, but could feel like utter trash to level because all of its damage was based on rDPS and your hugely padded numbers of rDPS doesn't help you kill enemies faster in solo content stuff when your initial burst doesn't actually kill the enemy. Again, this is due to the way % based buffs work, the higher level you go, the larger their impact will be and the smaller the effect will be when you're not with a party - which runs counter to its other identity as an assassin-like job identity of directly killing the enemy at the very start of the fight because you just lack that personal damage to do so.
A big reason why I play PvP for Ninja now is exactly because it captures the assassin-like job fantasy while giving into some support flavor through debuffs & utility that can affect the battle (afflicting heavy, stun, able to shield + gain movement speed, healing, gap close + stealthing mid-combat + assassinate, etc.). Unfortunately, not all of that can be translated well in PvE due to balancing issues and debuffs largely being ignored. So yeah. Mixed bag for me.