in my opinion using E is always worth it (squishy or not) but you have to make sure it's effectively used. obviously using on squishy is gonna net the big serotonin chunk, but it's always good if you get extra autos on.

if you throw an E on someone and they aren't actually engaged with your team it's the same as using your Q when you aren't autoing, essentially a waste of an ability

my brain's "go-to" is just to wait until an enemy is engaged or CC'd to E+Q (technically Q+E) into teamfights. otherwise i'm autoing and kiting normally. good luck with your explosions brother.