Indeed but the literal only reason I made a 99 DH was the difficulty in actually getting one out of the Starting Zone pre-100. It just becomes yet another DH in SL.You can have multiple DHs on the same account, just not same realm.
Fairly certain the lowest level is 48 to get the quest(or at least it was) to unlock the phase. Otherwise your just in the old northrend phase, and can't access the bosses without an exploit. Even then, I am uncertain if you would be able to loot them.99 will be 39, better off than the 101s and 100s going to 40 at least
No idea how the current 99 epics compare to gear you can get in SL
same with what a 39 can do. But still probably better off than the 100-101s and probably even the legion 110s
if you can get prepatch Icecrown high ilvl gear it would make for a cool toon. Though I’m not sure if you can get them on 39(you can on 49)