Level 1 selfheal. Don't max this. Its rubbish.
Level 5 healing turret. Max this. Best Guardian defence skill. Try to fight inside your heal beacon AOE.
lv 5 archilles heel. Max this. Best Guardian offense skill.
lv 1 shockwave to push those assasins away.

Use the bow with the longest cooldown. 1.4 or 1.6 secs i can't remember.
Equipment loadout is Gun, Gun, Bow. Don't use Shotgun.
Slot defence gems only. Buy Defence rings if you want to spend RM10 cash top up.

Hold down your left mouse button to Fire your sub-machine gun, double tap "switch previous weapon" (default is Q), you will shoot out a bomb arrow while firing your machine gun. Wait for bomb arrow to cool down, then double tap "switch previous weapon" again.

Assassins and Tankers will rush to melee you. Let them eat a faceful of arrow showers.

Follow my guide, my young grasshopper, and you will be MVP every match.