Crusader's definitely doable. It's really RNG-dependent, but the only reason my most recent run lost was because of a misclick death. Thanks to martyr, I had GG and pactmaker available from level 1, which alongside a platemail find meant I had 40% both resists by the 3rd tower. Momentum was excellent for getting over damage thresholds in the early game where I didn't have the sensation stone, and the immunities as always are excellent. Had quite a bit of blackspace and bloodpools left when I accidentally clicked the dancing blade who was next to the stairs instead of the stairs themselves, and the only affliction left was the "ravaged by forces" that means nothing for a crusader - I likely would have been able to kill H with ease. Sour about the loss but glad to see that my efforts over the past 6 months haven't been in complete vain.
IMO, the classes that might be able to complete purist VGT are bloodmage and transmuter, but since I suck with both of them I'm not going to try wins any time soon.