Nobody said Skarmory without SR. Even so, it's far from useless. Try posting EV spreads and the role each member plays in the team. In this way you'll find out how to play better (not just brute force) and help us with suggestion-giving. Anyway, Steel is an easy monotype to use. So many options!
Currently your team is so weak to ground attacks, Skarmory could save the day.
The way I see it now, you have 4 guys doing the same thing: bulky attack.
Heatran stays. Make it a specially defensive tank. Give it lefties.
Bisharp is a great option as a fast sweeper. Works wonders with lum berry.
Skarmory will be your physical tank and/or SR setter. Rocky Helmet.
Now you have lots of nice options to use: M-Metagross is huge for every team. Usually the opponent needs to sacrifice 1 or 2 pokemon to get rid of it. Gives you momentum.
Magnezone with a scarf is also nice. Make sure it has magnet pull. Otherwise use Analytic with Air balloon/Specs and full speed.
Specially offensive Lucario is a powerhouse that deals with any problem. Life Orb or Expert Belt. Also priority.
Empoleon is another special attacker that can absorb fire attacks and use SR, Scald and other utility moves.
Scizor can be used in many forms. Mega, Band, SD, Life Orb, Defogger, etc. Works like glue.
Another Scarfer that works wonders is Excadrill. Can work as a rapid spinner too.
If you decide not to use Metagross, Jirachi is another guy that can be unpredictable, or just go for the paraflinch.
It all depends on what you want to do.