LM can be overpowered in M3. In MT it's not because you can get easy map control, so feeding doesn't really work. I definitely don't think it was broken in MT, if I said so that was stupid.
In this M8, I can't see LM trying to be offensive any more than M3, so it's going to be the same thing as there except the other team's going to be more powerful as you farm up thanks to assims. As I said, I could be wrong, but I can't see a LM do anything useful for a team before 30 minutes in. At the very least the M3 Volt+LM sit in base for 45 minutes isn't going to work, thankfully.
Re: medics/self attacking.
It's really not easy to suicide them into enemy cannons against a good team, most of the time they just get hoarded in your base and don't do anything. Given that there's an incentive to actually seriously push now, they'll probably just end up being feed anyway.
Keep in mind that killing your own units doesn't give you any kill score or exp.-- As for the triggering of that, you just need to make it so that it doesn't auto-ally yourself, only your teammates. That should work...
I agree invincible isn't too brilliant, but I couldn't really think of anything better that fits in with Medic. My only other thought for buffing the Medic's spells are making the L1 medics useful for something: turning them into marines, returning 5 mana after each spell per how many are near you, etc. Anyway, I guess I'm fine with seeing if the Medic is still balanced without FH, I just don't see how it possibly could be. Maxx seemed to think that Power-L2 medic was viable, I can't say I agree because it's so hard countered by Mech, but no harm in finding out. But I'll say start brainstorming.
In the (admittedly few) games I've played recently, Lurkers is far more common than Melee. Are you saying people are going L2->L4, or just stopping at L2 and going HP/Mana? I guess Lurkers might be a more common M3 build since the games tend to be a lot longer, whereas your version has normal assims. Either way, don't give the Assassin instant teleport back, that was a very powerful spell in more than just the Mutant vs. DT matchup. You can force people to blow spells and get out safely.
As for Assault L4: Fire Wall... CAFG, I'm sorry, I should have just said "Fire Wall" assuming everyone knew what I meant, and confused everyone needlessly. Do you really think I give a shit about credit at this point? It actually is a pretty cool spell, I think it could work well and be both versatile and powerful. But let's see what Moose thought up.
As for Marine L4 Nukes: Do you really think it's going to be worth it to spend 240 mana (assuming your first ghost doesn't die) to take out 3 cannons? Especially since 9/11 classes can kill a cloaked ghost, I can't see it being viable. If you get caught once, the price for the 3 cannons jumps up to 440, and you can be damned sure people will be on the lookout after you nuke somewhere once. You realize it takes 2 nukes to kill cannons/pylons? I think you didn't understand this last time. Again, I guess we'll see.
One small DM buff I forgot about (I'm not sure why you nerfed it in the first place): Feedback to 60.
None.