As far as I remember Howl sucks and that's enough about them...
Indian is a drone/stoner/sludge kind of hybrid and not similar at all to Mastodon or Baroness unless they've drastically changed from the material I've heard... reminds me of Grief.
I do like the Indian I have heard though. I remember The Unquiet Sky being absolutely filthy buzzing droning sludge metal of a pretty high standard.
I get bored with most sludge metal and the fact it sounds exactly the fucking same, whether it be the dirty southern kind or the post metal kind. Exceptions exist though, Eyehategod, Isis, Mastodon, Baroness (recently) Kylesa. Most of the others fade quickly in my mind.