Solo a cactus? Yes, doable with less than 1000 HP. Stop 1000 Needle? Why yes, possible. Stun? There are stun, example Leg Sweep. Interrupt? Battle Regiment will stop monster from gaining TP in the first place, no TP = no shiny move. Monster already have TP? Heavy Shot/Twisting Vice, bye bye TP. In fact I solo Little Apkallu and they never ever Sleep me again, they don't have TP to do that.

Mobs in FFXIV actually do respond to players up to some degree. Djigga will never AoE if you don't hit them with a Weapon Skill. Dodore Minion will not Tail Whip you if you don't hit Weapon Skill (Which is the main reason why a THM can solo Dodore gang, Tail Whip > all other attack). In return, there are many effect players can do to stop mobs. Ever fight an NM? They are all cake walk mainly because Battle Regimen and the like heavily affect them. For example Great Buffalo, with BR you can stop it from gaining TP and all it do mostly are just normal attack. Then you can break it horns and it can't use its Horn special attack, incapacitate its leg and it can't stomp. People don't bother with normal monsters though, because they die too fast.

The point is, the combat as it is now sucks, because fights are too easy and mobs die too fast.

P.S: I beat all the bosses in FFX. Zanmato > boss, lol. One hit KO bye bye move.