Today's Daily made me think a bit about Rats and GG in particular (and, to a lesser degree, about Rats and TT).
Thoughts on GG:
* The whole inventory bead clogging aspect of GG's Boons is normally deterring folks from using him. I used him sometimes for pretty much just the boss-fight Protections, as by the time the beads fill up the inventory, you've already gained up to 200% refill for both bars, at an up to 135 piety cost, which normally means you gained some piety by extra conversions and normally you no longer miss the inventory slots the beads block.
* Humility is almost always a good boon, though Rats don't gain nearly as much benefit from it as other classes - the Rat levels up mainly for the health bonus, the base damage and corrosive strike is not so huge; however the loss of health regeneration hurts a bit. That said, more XP means earlier leveling, and higher max-level stats. I normally take it early, but I can see an argument for taking it late - or not taking it at all.
* I thought about another use: beadless Enlightenment. GG's piety gain is generous, and especially in light of how front-converty Rats can be, it means 100 piety is quite achievable by mid-game, expecially if not a lot of piety is spent on the other boons. 100 piety for +5 Mana alone is normally considered to be too much. But I think that if you're not in a hurry to spend piety on other things, then - especially in light of the shorter Rat mana bar - it's not such a bad proposition. Also, if it's unprepped GG, your piety will fill back up to 100 quite fast afterwards, doing pretty much nothing, and then you can still do the Protections angle for the boss-fight.
* One more thing that came to mind, and this might be a bit more complex, but basically if you don't have any must-have prep items, then you can pretty much prepare for an Absolution surge and then use his punishment to clear away the beads. Like, if you go in with full preps, then just the 3 extra potions and the converted early items will give you 25 piety, which - with the on-join piety - gives you the 30 needed for 5 shots of Absolution; and then you can just quaff the other potion at zero piety to get punished. You lose the beads and the 1% magic resist, but you retain any other benefit (i.e. extra health).
For TT, I think the solution is to only join TT when the character is relatively high level. Hit a lower-level monster once to corrode it; then use magic to deplete its health to get it within one-hit range; and then kill it without having to worry about retaliation thanks to strike order. It should fuel the piety flow and that piety can be spent on the needed boons (most likely, Learning or the Reflexes potion combo). If TT has been prepped, or has been angered, this becomes more difficult to do, though I can also see some merit in pre-corroding monsters (and not worrying TT punishments), then using teleportation magic to get the monsters nicely prepped for the kill, and then building up his piety in chunks, always taking out enough slowed monsters to get the next boon you want, spending all your piety and making subsequent punishable actions irrelevant. Also, he gives +3 piety for a successful dodge, so picking up the Dodge boon can also help the long-term piety economy a bit (as in 10% of the cases you'll get +3 instead of -3, so per-strike piety penalty drops from -3 to an average -2.4 piety). That said, TT remains quite dangerous, because after he has been angered, it becomes next to impossible to get large chunks of piety under him unless the player has a way to spam WONAFYT for example.