Welcome to Librarium Online!
So I've been running a 10x unit of Hellions with the Baron, and it is a killer squad. 5/5 of my last competitive games have focused heavily on what I did with these bad boys, whether it be holding an objective in cover till turn 7 (stealth+go to ground=2++cover), assaulting and holding down a flank (Baron is S6 on the charge x5 attacks), or literally dragging the opponents hq character across the board in sadistic display of gloating (did this to a nurgle army's Typhus character, his poor terminator body guard chasing after him).
They're quite durable as well, having been 'lashed' out of cover, lit up with a search light, and subsequently fired upon by two battle cannons and rapid boter fire. They were then assaulted by a greater summoned demon and hi dreadnaught crony. In the end only the Baron was left (thank you shadowfield!), but it was killpoints and a single 170pt unit of Hellions had tied up the middle.
Definitely very versatile and hardy Troop unit for <275pts. I'd say their drug roll half dictates what you use them for, depending on the rest of your list's build.
On a side note, the new models are fun to build and definitely add a dynamic look to my army.
how did you convert the Baron?