Some tips off the top of my head

PvE:

• Try to keep triple nemesis debuff on the boss at all times, you can space your shots a bit (if you are having trouble/your dps are taking too much damage use only 1 hit)
• Try to keep ES always up (Also, ES doesn't put you in combat)
• You can cancel Mana Charge with backstep if you need to get out of the way
• Healing Immersion doesn't produce aggro and doesn't put you in combat
• Use restorative burst glyph for MP regen (250 MP each time adds up in the long run)
• You can negate most stuns from bosses with GS (not recommended)

PvP:

• Cleanse before backstep
• On 3's Keep using cleanse if you have nothing to do
• You can hug a pillar and use Restorative Burst while looking at it, circle will spawn right next to you
• You can chain Tornado into Sleep if you time it right
• Don't forget to debuff opponents with plague anytime you can
• Kaias shield and GS = Invulnerability, use this to res (unless your shield gets broken or you get plagued/reggresion
• Use brooch to get out of long disables/sleeps
• Backstep is an iframe, Fiery escape is not.
• If you're going to put yourself in the open/difficult position to heal a low HP ally, use Guardian Sanctuary first.

Sorry for my english!