So I've hit 50 and started getting into I guess end game content and there is a few things I notice about the game at this point.
The combat lag severely impacts the game. I don't know if anyone else notices it, if it's input lag or what but the combat lag makes it too easy to place the blame on the game instead of being able to activate a skill ''on time''
I off tanked... If you can even call it off tanking Ifrit HM last night and holy hell if that's not the most shameful use of mechanics ever I don't know what is. I literally did nothing except auto attack with my finger hovering over the shield bash button waiting for eruption to pop up. Not that it's hard to stun him, but with shield bash being on GCD and there not being any Telegraph of the boss before eruption is cast combined with the fact that the cast time is faster than GCD and the combat lag, it was pointless to put in any rotation of abilities for fear of missing that stun.
This isn't just a problem for Ifrit HM I've had this problem throughout the whole game, if they are going to make bashes a mechanic for boss fights it needs it's own GC.
Buffs that will not persist through death are another issue. I'm sorry but I am not willing to purchase food that increases my stats and then have it wear off after a death, if you want your player base to be throwing themselves at walls in dungeons you can't expect them to sink money into stat buffs that expire after every death.
The other major gripe I have is what has already been mentioned is the reliability and effectiveness of threat generating abilities. First off provoke is a joke, it should apply a focus debuff that lasts for at least a couple of seconds forcing you to the top of the threat list and giving you a chance to regain control as the tank, it wears off too fast and allows dps to steal threat, I have to provoke and shield lob and usually run over to the target and start my combo on it before I can regain control.
AOE tanking is god awful. I cannot comment on warrior AOE tanking but as a paladin forcing me to tab target and spam flash is not an effective way of doing this. One simple solution for paladin at least it's to add emity upon a block, there you have multiple targets attacking you, your generating threat on every block to all targets, still forcing tab targeting if dps is AOE but not locking you to it every engagement.
There are other issues I have that I'm sure will be addressed over time but I must admit I'm not familiar with SE and their understanding of mmo mechanics, I know this isn't their first one but I would argue that since ff11 the mmo landscape has changed drastically and I don't know if I have faith in SE to grasp this long term.
Tldr fix combat lag.
This is one case where I definitely think they should take some cues from WoW. Stuff like off the GCD interrupts, group wide food buffs, and simplify picking up mobs a little bit.
It can be pretty rough with a shoddy tank that I have to heal shortly after the pull, and rip aggro immediately, and once I have it and start having to heal myself to stay alive, they usually aren't getting the mob back.