Congrats!!!
At first I misread Vicious Steel for VGT so I was really shocked (I don't even know if Purist + VT is doable in VGT).
I'm less shocked now that I found my mistake but I'm still very impressed nonetheless.
I'm especially impressed by the choice, Berserker is an uncommon pick for me, and Halfling even more, and I would never have tried to beat a Vicious Dungeon with a VT+Purist.
Yet I rainbowed NC and VGT and got VT in other Vicious dungeons too.
I'm confident that this is just a question of time until you beat DL + VT (unless you try it Purist too)
I have no recollection of which strategy I used sadly.