When a mage goes to assimilate it should only drain half of what they got.
Example: Tech mage max assimilation - 18 energy, goes to assimilate opponent the opponent only gets the deduction of half so it would be 9 energy in this case. If its uneven like 5 energy then it should round up and deduct 3 from opponent.
Or put a 4 round cool down for assimilation and maybe a 1 round warm up.
Assimilation was originally like your first suggestion meaning it used to only give back 50% of the energy drained to the user. Personally I would love to see them undo the 100% energy gain and make it 50% again.
As for the second suggestion I don't agree with it. I remember in certain cases especially against EMP builds that go first using this move was needed to get back some of the energy back from EMP.