Does burning stack?

say i use incendany bonds (3 sec burn aoe) then rodgots invocation (3 sec burn aoe) does it add up too 6 sec burns or does it overlap and only does 3 secs?

it will reset the timer, if your timer was at 3 seconds it will reset it to 3 seconds, ie...overlap

Nope, burning is a condition, and as such is only renewed to 3 seconds. TIming your spells so you maintain continuous burning without overlapping and wasting damage is one of the more important things for a fire ele.

Nothing stacks: the same condition, the same hex, the same enchantment, the same shout, etc.

You can stack multiple conditions or hexes to max out degen or stack multiple enchantments for regen - but they have to be different skills. You could "stack" multiple Life Siphons on different opponent to give you multiple regens.

Get the idea?