Have either of you actually played the beta at 120, or watched streams or videos of it? Every decent level M+ on the beta has a DH tank in it. The ones that don't have a BDK in them. The other tanks are not really present (except Sco on his warrior because he loves warriors, but I don't expect him to actually main one in BfA, as they're just not strong enough).
It's all well and good to do some form of forum speculation, but the reality is that DH has been the beta fotm m+ tank for well over a month now, and nothing has changed on live. The fact that they now have purge, 5% magic damage debuff and the highest AoE damage by a landslide alone makes them worth it, and that's on top of AoE CC, AoE silence, mass grip and absurd mobility.