I just took the most basic approach to my current spawning character. Since I normally do spawns in wraith form for mana leech, I just replaced 100 med with 120 focus (I had about 30 skill points free).
I'll tell you in pvp how my mana regen is. It would be 10 MR with 100 med and only 6 MR with 120 focus. So i can make up for the other 4 somewhere else.