To make it easier, try and get the best gear you can atm, grab a full set of AE, load up on myrrh, grab both stamina and willpower food, alchemy potions, glue bombs, find guildies to give you Aura of Fortitude and AoR(energy or mana depending on which you use). Grab church pots, or if need be, elixirs to keep you alive.
Rest between every trial, make sure all your buffs are always on.
The only really challenging fight is the last one, the first 3 are trick fights anyway.
Always use the abilities you are given, those are ridiculously OP, and can save your hide.
For the first trial, Sarn is a tricky [I Have a Potty Mouth], but he's harmless once faced properly. Just use the chain ability on him, kill the mob he spawns, rinse and repeat until you killed the red ring spark he summons.
For the second one, either tank or kite the orc cultist till his shield buff drops, then zap him to oneshot him into oblivion.
For the third one, run around like crazy. Forget any talent of your own that's not defensive, crowd control, or heal. Use the abilities that the trials give you to whack mobs and stay alive. Also, run into those blue and yellow orbs to get new abilities or temporary buffs.
And, for the last one... this is the only one that's actually a problem. The first mobs are easy, until you reach the Parasites, the huge centipede-like things. Those two mobs are manageable if you have aoe, or a good dps output. If not, try kiting a bit and keeping your health up. Mind you, if you have any long cooldown abilities, now is not the time to use them, the next fight is even worse. Try and survive them however you can.
Finally, the demon at the end and his two hounds. Focus fire the hounds first, and throw a glue bomb on the big demon. He's immune to CC but not slow, I've double checked with summoner Howl of Death and the healer's slowdown rubies from Holy Rage. He's kitable, and that's the only real way to kill him if he's more powerful than you can handle.
If you have any convenient nukes to use at him, try timing them so he doesn't hit you. If you have a pet, let it tank for you. If you're a scout, use recoil to keep your distance. If you're a mage, use flash to keep distance. Healers, holy rage slowdown + bubble. Psi has temporal acceleration and ecto, you could try burning him down, as I'm not sure how abilities stack against him. Warriors/paladins, consider shields, or going pure raw dps and beating the daylights out of him faster than he can do the same to you(or getting speed pots and taking short breaks to regenerate). Bards? I haz no idea really, haven't played the class, but you should still have enough hax to beat the guy
After this guy is down, you just need to survive a short, short bit as Nihaz blasts the demons, and you're clear.