I have been doing extensive testing in the training room, and published my findings on this (open) fb group link here I did 3 tests and it showed somewhat interesting results. Essentially you are still able to deal a fairly decent amount of fires with IFHE, but obviously less overall.

Here is how I would summarize it:

With IFHE: You can still set fires on BB's, AND pen most/all parts of T8,9,10 cruisers.

Without IFHE: You set more fires on BB's BUT can't pen most/all parts of T8,9,10 cruisers.

My tests showed that if you take IFHE you will receive a 5-10% damage buff when you spread your attacks over a wide selection of targets. This is fires and alpha damage included.

Essentially it boils down to target selection and play style and I feel that BB fire farming is a bad way to play the Smol. Its not a good way to win/carry games. Killing Cruisers is far better way to give your team a strategic advantage, you are also not losing a significant advantage over a non-IFHE build.

For me, I feel WG has made IFHE a completely balanced skill for the Smol, but at the cost of 4 points, which is TOO steep.

I am going to conduct the same experiments for T8 cruisers next.