Here is what I do with my Mesmer in PVE. He's my main character and this has worked through all of Prophecies, Nightfall, and I'm working on Factions now. I'm a Mesmer/Monk
Empathy
Backfire
Conjure Phantasm
Energy Surge
Power Spike (I intend to replace this with Echo to Echo Lightbringer's Gaze/Energy Burn or Surge)
Energy Burn/Lightbringer's Gaze (If engaging demons in combat)
Heal Area (Quick self heal that doesn't rely on there being an enemy to target, like using Ether Feast)
Rebirth
I have 15 Domination, 11 Illusion, I think 9 Healing Prayers (enough to put Heal Area at 110 HP), 7 Fast Cast, and two leftover in Protection Prayers.
When I go into battle, if there's a cleric, I cast Backfire on him, cover it with Conjure Phantasm. Usually kills itself with it's own healing spells, Backfire does 140 damage. Empathy on warriors or dervishes. When it recharges, Backfire on any eles or other casters in the area. Energy surge and Energy Burn for quick spikes. Up till now I've used Power Spike if the opportunity presented itself, but I'm not too good at that and usually I'm too late, so changing that up for Echo is something I plan to do soon. Heal Area if you need a fast heal and Rebirth when saving the party from a near wipeout. I've saved many, many a party with Rebirth
EDIT: For the last guy who asked about Illusion Builds while I was writing my post. Generally, I've tried to use some Illusion spells and mix it up like that, and I used to be all about Illusion back in the day, but I've found Domination is just much better for slaying. It's easier to go with than Illusion since the degen is usually never realized on a monster.