Can someone give me an in-depth explanation why Summoner is arguably the worst DPS?

[Lyrica_Ashtine]

Ouch, that direct assault on a poster, rather than the topic without proper elaboration. So since you asked for it, here it is:

BLM:
manaward - very meh only reduces damage by negligible amount, by comparison second wind destroys it and it is only applied to the BLM so not a party utility.

You compared it to Second wind in one post and in another post you're saying it's useless because 7 out of 8 still take damage. With the previous argument you provided: All melees and bards (and even warrior) could just use Second wind. In this case, up to 5 players will take virtually no damage here by your logic. That equals 5 players having a useless cross class skill. By the logic you provided anyway. That's not a really good argument to elaborate the usefulness or utility of an ability.

Additionally, second wind destroys it? A cross-classed second wind heals for somewhere between 400 and 900 HP, depending on gear. While on a low level black mage, Manaward blocks off 1000 damage with a 3000 HP pool.

Manawall - alot better then manaward as you can use it for earthshockers etc but same as above helpful but any other dps can deal with the mechanics with heals or good timing e.g. titan LB on adds etc

It's interesting how you bring up T13 mechanics as an example for manawall, but not for manaward. Manaward could save your own life for multiple scenario's. Especially for those where weakness is a factor. Sure, you could argue that no one should be dying in the first place. But one death does not equal instant failure.

And oh hey, surprisingly mana ward -could- save you from potential deaths where second wind cannot - Specifically for rage of bahamut or marked megaflares+tower combo.

Lethargy - works on little where it matters usually overshadowed by miasma

Where lethargy won't work, the disease debuff usually won't work either. Please don't forget about that. They're not even the same thing. Lethargy gives the target a heavy and slow effect while Miasma (II) gives them a disease effect instead.
Also, miasma itself doesn't reduce the healing or movement speed. It's the disease!

Stun - its a stun nothing more needed.
Blind - its a blind nothing more needed.
knock back- " "
DPS without having to target - on fights like levi, t5 etc the DOTs still tick when you are unable to target them.
Tri - Disaster - the more useful of the useless binds

Stun is not a very good argument here. Most targets where no stun-control is required is immune to stun and on targets who do require stun-control you may not stun either way.
Blind is hardly effective at all on 99% of the targets where it matters. Immunity towards it is build rather quickly too - Same with Diseases.
Knockback usually causes more harm than good. In cases where it can cause no harm the target is immune to knockback.
The DPS thing is the only one in this list that's somewhat correct.
Not that bind is a very useful utility at all, but it's not like Tri-disaster is that much better than freeze - Neither get used in practice anyway.

I'm also not sure why you think an arcanist eye for an eye is superior than a cross classed one. Or the very least you are making the impression it's superior. It has the same effect, with or without passive. The only difference is the recast duration.

PS. I don't recall doing anything ever with you