So is a 250-ish average score alright for a rdps starting out with Withered Training? I try and play carefully, pulling small mobs or single targets, keeping my Withered in ranged/follow mode and only push the "oh shit" button when I'm facing the arcane mobs and my interrupts are on CD but it's basically a war of attrition. I try to get out as much damage as possible as quickly as possible to hold threat and use my two interrupts where appropriate but I still tend to lose units no matter how careful I am with pulls.
I basically can reach the same point where Leystalker Dro shows up (or he's always shown up in the same spot for me) and it's game over for that particular run. I've started just expending what Withered I have to take as many chests as I can in hopes of getting more item buffs for them (they have 35% more health, no longer run away when wounded, etc.), even if it means ending my run early.