It's less that WAR mains complain for buffs and more that they want their main niche preserved, that of being the best tank for DPS, which was not the case in 4.0. PLD was ahead of them in that respect on top of having more utility. Their 'complex rotation' was really just the stance swap penalty (which shouldn't have been a thing to begin with, as it took away from both mitigation resources and damage) and the IR window halving beast gauge costs instead of nullifying them. Yet it also had a longer duration, and higher potential thanks to syncing with every other Berserk, which still had a raw damage bonus (This was fine as it actually made managing gauge interesting and balanced out the higher potential from Berserk at the time). The main reason that's the case is because the role action changes took more from DRK and PLD than WAR. The secondary reason? People don't rely on tank stance to mitigate damage anymore. WAR's Tank stance is supposed to be the worst one to begin with and that isn't even an issue for them right now given both of the other tanks can use abilities on the WAR to avoid needing to use Inner Beast.
The unfortunate consequence of wanting to maintain that niche as the best raw DPS tank is they wound up being the best overall tank due to poor raid design and lack of forethought on SE's part regarding buffs. The problem with what SE did is they went too far in 4.1 and gave WAR everything they lacked, without toning back what they already had over the other two tanks. Shake It Off was a dumb rework. The IR/Berserk changes are a toss up but I see the merit in the direct crit change. The 'free Fell Cleave Spam'? Not so much. I dislike the Role Actions more than anything though. WAR got way more out of it despite losing Bloodbath. That's the part that needs adjustment.
DRK's problems stem from their complexity (mostly boils down to fight to fight variance) and their reliance on sustained dps compared to the other two tanks. Dark Mind makes them the best or worst tank when it comes to mitigation too. They don't have a real burst window as much as a collection of oGCDs that barely constitute something similar. If more weight was put into their oGCDs that problem can be shored up, but really I think they need a spike damage window, probably once every two minutes, alongside that in Shadowbringers. Otherwise they're just going to fall behind even more. They're the best tank when it comes to AoE right now too and that didn't really get a chance to shine due to the focus on one-boss fights. Though given people are calling for a flash upgrade too I wouldn't be surprised to see that niche taken away. Hopefully SE lets you use more blood abilities at the very least.
I'd consider Stormblood a complete failure in regards to tank balance and mechanical theming. They all require more work next expansion and with Gunbreaker coming in as well that leaves less time to devote to the other three. I hope that means SE is focusing more on them just in case, but we'll see. I hope SE at least makes tank stance matter for whoever's tanking the boss. That would fix most of WAR's issues given how healer balance is currently.