Instance Bosses Tactical?

I'm new to this game and I was wondering how are instance bosses in here. Mostly talking about challenging/tactical.

Read some stuff a bit and from those I read they are mostly just tank'n'spank with some additional AoEs but nothing special.

Well I don't really care about low level bosses as they are mostly power leveled from what I understood but the end game bosses that are farmed, are they tactical and interesting?

I'm not talking about tank and spank: by this I mean, just tanking the boss, damaging it and heal its damage, maybe interrupt an AoE or outheal it and that's all. This is what I mean by tank and spank

What I mean by interesting is NOT the above, but something additional needed for every boss, like avoiding some stuff (adds/special attack/AoE/anything :P), killing something (could be adds) fast, etc. Like this other MMO I played, there were many interesting bosses, one of which very 'complicated': you had to drag and kill 6 adds in some specific spot (adds were named with a color and those spots were shining with a corresponding color) to spawn a circle, then after a few seconds everyone was getting a debuff with a random color that would kill you instantly in 10 seconds if not removed - to remove debuff you had to run to the circle of that color. There was more after, adds coming 1 by 1, that had to be destroyed as soon as possible, because in a few seconds they would disappear and give a nasty stackable debuff (-10% damage per round) and some adds were immune to physical and some to magical attacks.

Is there something like that in here too, or are mostly based on tank and spank?