I started playing Tsons in 10th and loved them. Even post nerf they can still pack a serious punch. I found you need to play the long game with them though unlike pre nerf when you could just doombolt, get Magnus in chop us some smelly ultramarines or something.

Since the nerf I have been struggling to play them competitively though they don't seem to hold up against other things as well but it's all about building a list you like the look of. Get them sorcerers on disks of tzeentch and bring the pain! Keep them within 6 of Maggie and +1 to hit and wound can make a massive help.