hmm mby its not bad to kick scizor or lucario, but still as i think you dont need Steelix when you have Aggron (or Aggron when have an Steelix):
Steelix is Great against physical Fire poks but still dont work well on Fire/Fight:
Steelix: Stealth Rock, Roar, EQ, Ice Fang
Set up SR hurts Fire poks on soo many lvls, also do STAB EQ but it dont hurt Fire/Fight combo as much. Mby with sturdy he will be able to 1hko them not sure.
Aggron on other hand can do same work: Stealth Rock, Roar, Head Smash or Stone Edge, Heavy Slam. With Sturdy will for sure 1hko them cos of manly Attack power.
Set up SR, Then Roar main threat, and high chances to 1hko many pokemons with 2 moves
For me Aggron is superrior to Steelix cos of power. For sure both can Suicide to takedown main threats, and make at last 4v4 fight. But its up for GL if they want play like this. On other hand it can be supprise for ppl, and punish them for a picking brainless fire poks, and make hard time for them in 4v4.