Ignite Proliferation Support + Berek's Respite

Bump, I'm noticing the same issue.

I wonder if it's working as intended. Respite + Exarch spread is definitely worse than only Respite :/

this is not a bug, ignite spread isn't ignite prolif. I'm the guy who put Maw of Mischief stone golem elementalist together so I did research on this back in scourge

ignite prolif. -> creates burning area once ignited enemy dies, secondary kills do not create their own burning areas because the area does not ignite by itself

ignite spread -> ignited enemies that die pass on the remaining ignite on enemies in radius

when you run both, occasionally the burning area from prolif. will kill enemies that aren't yet ignited and thus prevent ignite spread on other targets near it, breaking your chain reaction.

It only really became an issue when they nerfed the spread radius on berek's respite. Anyway, don't use ignite prolif., if you have any generic aoe increases or don't level the gem too much if that is an option.
Berek's radius is speculated to be ~20 radius now so all eldritch implicits are inferior; you want to run the ring and ideally not use ignite prolif.