Isnt this what web grenade is for? M30 w/ kd conversion proc? Buckshot w/ kd conversion proc?
With the 2 sec animation, and these fast cast options, it is trivial to keep some (most?) of your targets on their back/immob while you light them up with ignite, and still pump out damage. Two of those powers are in ar proper. Toxic web grenade is in /dev, and has a 17.88 sec duration on the immob before slotting. (ar/dev, kinda an oldschool thing :P)
For aoe effect, you get glue arrow in a secondary, dark pit, ice patch, throw sand, various holds. All of those provide a modicum of immob-ness in an aoe that will allow you to apply multiple stacks of ignite.
Even better, you get a st immob at level 1 on all blaster secondaries, which can be used at range to dump multiple ignites on hard targets.