I have to say this is a major killer for me in MMOs. The only reason I'm playing FFXIV is because I like the ACN archetype - a range caster with a cute pet; unfortunately they took away my Carbuncle post-Lv30 -_- (an atrocity I hope they will remedy in Patch 3.4).
There is at least one mob in game that doesn't telegraph. The Diresaurs @ The Churning Mist have a huge attack with a very obvious wind up animation but no telegraph graphics.In 4 man, they do more damage, and the telegraphs are all gone. You have to pay attention to animations and make educated decisions to stay alive. As a reward you not only receive more loot, but better loot.
Not really for or against either system though.