For an idea for a ED l4 attack, you could have a scourage spawn. This scourage will have a movement detection trigger on it, much like the way footsteps sounds are made by units walking (i.e. Aliens, Resident Evil One). When the scourage moves, archer companions will spawn invincible and burrowed underneath the scourage and will instantly unburrow and attack. The l4 would last about 3-5 seconds of scourage movement as the minimum time of use, up to 8 seconds or so, of scourage idling.
So triggers for the timer would be like:
Timer of 60 DC's,
While scourage is moving trigs = Subtract 2 DC's
While scourage is idle = Subtract 1 DC
This way you have a set timer of no greater spell time of 8 seconds, and no greater than (approx.)3 seconds of full use of the spell.
This would encourage people to keep the scourage moving to have the spell look and preform to it's fullest effect.
The end result would look like a stream or hydralisks unburrowing towards it's enemy, and firing.
You could also pretty up the spell with deaths of units, like spawning critters under the scourage, he same time it makes the hydralisks, and kill them so it looks like the earth is erupting in a line. (Btw, that could be the spell name, Eruption) Then afterthe spell is finished, all the arch companions could die one by one in a really fast manner.
The medic's l3 could be like a "reverse curse" for teammates. Instead of mana all at once, "tagged" teammates would slowly gain mana faster over a while. The spell effect should have a long effect time, but a slow gain amount to justify. THEN, the spell could be stacked, allowing for a faster mana gain over a fair period of time. This would create longer spell effect, so instead of nearly full teammates only replenishing like 25 mana, they would be able to get mana for a much longer while and start to go on offense.
Medic's final spell could heal in increments of 20 as you have stated, with the option of sacrificing 25-30 medics for full heal. Or, Medic could heal the teammates according to however many medics they have to sacrifice. 10 more medics = 20% or so. If this seems a little to summoner-ish, summoner's l3 could be replaced with something else, like turning all darkswarms into something, dunno.
Anyway, those are just some more ideas.
None.