why are taunt failures still a thing? Oh, never mind, let me answer that. Because it's part of the game!
because the game isnt perfect, nothing is perfect, and the frankly for that reason alone it should not be perfect either. If anything was a sure thing everyone would do it. The element of failure in any combat situation lends to the situation imo and the makes the player to rely on instinct and whatever else to better a bad situation. Casters have fizzles Warrior have taunt failures, why should us monks be any different on ability that can fail us in combat and force us to compensate to better the situation? and as stated here too there is always ID too, but still.
I just don't understand why we have to fight the mobs these days. You would think by now we could just look at them and they would die then just let Auto loot put everything in our inventory. And speaking of that why do we actually have to sell stuff.. can't it just convert to plat as it hits our inventory? Don't get me started on buying stuff... the game should be able to read my mind and just use my plat to get me what I want at a very cheap price. Just saying. Just don't understand why these are still a thing.
I suspect that the real answer to the original question is that spell fizzles, skill failures, the randomness of each melee round/crits/resists all combine to make each encounter unique and unpredictable. When dealing with trivial content it doesn't matter because you'll win even if the RNG hates you that evening. When dealing with gear-appropriate content it makes encounters challenging and, hopefully, more fun.
Gate, secondary gate, and tertiary gate can all collapse. Evacs can leave people, including the caster, behind.
This was fun once in the past when a wizard or druid I was grouped with used their evac for normal porting because "it is faster" without realizing it can leave someone behind. So a non-gating class got stuck in the middle of a dungeon with no way out because their group just left .
You only have a one frame window to hit block, takes a lot of practice to land that trick. Keep trying.