A lot of guides that I've seen tend to go over how to play AST in higher end content, where damage is very very important and people don't generally need the extra MP/TP (unless things go horribly wrong). At level 70 in extremes or savages, people generally know their jobs well enough to not need the extra resources. Everything happens on a rotation, and you account for your resource pool so there's little risk of running out of stuff.
In lower level content or dungeons? Spire and Ewer are absolutely useful, and damage is not necessarily of the utmost importance. You're not going to hit an enrage if you sacrifice a bit of a damage in order to keep the melee DPS spamming their aoe or help the tank maintain aggro.