I prefer Stratholme to Scholomance.

However, pick your poison between the two.
And run either from 45th to 55th.

At 55, migrate your team to Hellfire Ramparts.

If you want to boost beyond 60th, at 60th move to Underbog.

At 64th, move to your Auchendoun instance of choice.
I forget which one I used, but you want the one with mostly melee types.

At 68th, I moved to Steamvault.
Although Northrend questing might be better at 68+