Increase Perfect Strike Ignite Damage

Actually im playing a build with polcirkeln unique ring to have herald of ice explosions. Mapping is very enjoyable, but i have problems with bosses.

I want to use perfect strike with ignite against bosses, but the ignite isnt that strong. Is there something i can use, without investing nothing or to much in ignite, to increase the damage of the ignite with perfect strike?

At the moment i have following gems linked with perfect strike:

Searing Flame -> Window of Opportunity -> Fire Infusion -> Fire Exposure