Haven't ignite same priority as sunders, cos, coe? I thought they have and can't be replaced.
Main idea that we running in fire like 2-3 months (zg first, and aq20,40 than) and never had any problems with ignites. Our raid setup are pretty stable, we never limeted wlocks/boomkins/spriest in their abilities, also had some corruptions, dooms, etc on boss. so i guess there were some changes/fixes etc last week.