This is the way fusion works:
When going to level 2 it chooses the highest health and attack and adds +3 to that in the resulting unit.
When going to level 3 it does the same but adds +6 health and attack.
At least that is how it is supposed to work! I haven't been able to reproduce the automaton leveling problem myself, but I'll continue to keep an eye out.
Thanks for the heads up on the wrong numbers for the spiked helmet - that was an easy fix and I can hopefully push an update for that soon.
As for the altar beast problem when using the "on hit" distillation - I was able to reproduce this. I'm considering removing the "on hit" distillation in some way because it causes A LOT of bugs and edge cases with distillation (and it might just be way too powerful). Gotta think about it!
Thanks again for all the comments and bug reports!