Amesha's 4th ability makes you invulnerable meanwhile your energy bar is NOT full, due how high is the damage from any RJ enemy that means you take a single hit, stay invincible 1 sec and if you don't cast your 1st ability you die almost instantly, something that happens commonly when facing crew-ships. So the perfect way to fight using Amesha in any RJ mission is hit 4, then 1 and then 3. That way you will stay alive long enough to cast your 4th again when only 2 or 3 hits are left from your 1st ability. Get hit, energy will be refilled to full cast your 1st again. That's the cycle.
Amesha's 3rd ability slow down enemies. It's a toggle ability so you need to keep an eye on your energy bar or it will drain very fast. If there are no enemies nearby always disable it so your natural AW energy regen kicks in.