Steelix? Eh, i guess it's Sheer Force ability is nice, Stealth Rock is always appreciated, and it's mega form is good tho. But you'll still be lacking damage output, defensive oriented pokemon in Reborn aren't that useful, unless you're running a Trick Room setter, but still, it's better to have offense than defense, and there are far better options for the Steel/Ground slot, like Excadrill, and Aegislash, for example. It's worth saying that Steelix is really good, but only in the early to mid game, since it tends to start going slow with your progress.