It's not what build you use........(unless you are truly messing it up and don't know how to make a mage build. Which I find hard to believe since the rubies are pretty straight forward)
No it's not your build, it's your gear. The mobs in the Trial will be the same lvl as you, and if your gear is lagging behind, you will have a lot of trouble. So first thing is to make sure your gear is best possible. Additionally you should have Daily pots, Alchemy pot, healing pots/warden's AE, buffs like fortitude or potency.
And last but not least, learn each trial:
http://childrenofmidian.guildlaunch.com/…c.php?t=8775255