Note:
Humans can do the Spellweaving quest, and afterward use JOAT to cast as if 20 skill. It also means that they can get 4 non-spellweavers into a circle (etc.) and get a level 5 focus (6 in prism).
With the completed quest and the proper spells in book, Humans can cast
Arcane Circle
Nature's Fury
Gift of Renewal
Immolating Weapon
Attunement
Thunderstorm
I know from personal experience in Doom, a level 4 or 5 focus produces an incredible Gift of renewal, even cast by a person using just their JOAT. This is on the order of 8-10 HP every 2 seconds, plus an unreal duration (The duration is normally 50 seconds or 1 minute, for just the 20 skill (would be 5 minutes at 120 SW), but you get +1 minute per focus level).
The hard part is getting the non-spellweavers onto a pentagram down there for the focus, but they're a heck of a lot more common than people with points in the skill (a human can use people with either 0-20 or 0-40 skill - not had a chance to test yet)