ma have a self-buff that greatly increses your atk and atk speed last about 30 secs and by the time it ends you need t owait for another 30 secs to recast it.
its really nice for bosses and high hp enemies in trials.
however the ma doenst have spameable skills, most of the atk skills are to cause status like reduce the block, prevent heal and increse the damage recived, the damage itself and the cd on those is not that good.
on the other hand thief skills have quite acceptable cd and you can make chains and keep using dmg skills.
i would say the thief have better burst damage, with a couple skills can deal a big punch, but over time the ma with his charge stackeable deal more damage.
as for builds in any case go for critics, any other to me seems like pointless.
pump critic rate and critic dmg all the way up with gear, enchants, thropies, gems, etc.