Agnostic's Collar, some luck and *maybe* some bugs got me through Dragon Isles for the first time tonight.
Played as a human Berserker with Agnostic's Collar, Conjunction, Reflex/Quicksilver and some other stuff prepped. All super simple stuff anyone could prep, basically.
I was fortunate enough to find Tikki very early along with 2 shrines to desecrate which lead to level one learning. Other goodies I found early on were a troll heart and a Balanced Dagger shortly after I get my second learning for a total of +5 XP on same level enemies. As for the possible bugs I noticed I sometimes didn't lose piety after the first exchange even if I didn't dodge. Has TT changed or should I submit a bug report? Having the piety to get 2 pairs of Reflex/QS was very helpful against the Matron.
Balanced Dagger is one of my favorite shop items for Vicious dungeons. It saves you from having to figure out a way to kill higher level monsters. (Berserkers often do OK anyway, of course.)
As Avatar said, TT only minds if you take multiple hits from the same monster. So if you first-strike the monster because of your higher level, GETINDARE, or otherwise, you won't take the ding to your piety.
Good luck on your Vicious journey! Berserker/Dragon Isles is a good place to start, and now you have the Dragon Shield which is definitely one of the best preps in the game.