I think that is one of the big things missing from fighters is advanced tactics, faster cooldowns on trip/stun.. a use for sunder.. aoe trips/stuns with reduced % chance that is offset by tactic investment..
A fighter should be the one in a tanking position soaking up/mitigating damage while holding boss aggro.
Problem is fighter cant stand there and trade punches, they have to twitch and use cheese mechanics to avoid death.
Fighters have no definitive tanking/tactics advantage that puts them to the forefront when facing heavy hitters to mitigate damage and hold aggro
New mechanic design has many Bosses that don't retain aggro so a fighter has a hard time holding the mobs attention.
Fighters have no boss tactics like a 'stand your ground' tactic when toe to toe that increases PRR/MRR/heal amp/deflection/hate/saves by a substantial% the longer they stay put..until the fighter moves and it resets..
Kensai is lacking things like damage deflection.. a way to avoid damage like ranger two weapon defense, or a deflect arrows, wind through the trees, elusive target, stuff that reduces the chances of a fighter getting splatted when toe-to-toe.
They have no concordant-op effects that would potentially turn incoming damage into healing (barbarians have bloodrage)..a way to heal without stopping to chug pots, or require a heal spamming babysitter...
A healer should be able to heal the fighter with minimal mana healing demand since they are supposed to be built to take vastly reduced damage while putting out damage...
Fighter feats while improved are still lacking..
Game mechanics have changed , we don't have long duration fights for better rewards.. like LOB 3 rounds for more chests.. instead we have mass brute zerg dps, dump mana bars and kill as fast as possible for the win..
Long duration fights lead to failure.
Ultimately fighters are lacking that core aspect of being able to wade into melee while requiring minimal healing to keep them alive... the class that is expected to wade into melee and be the center point of combat..