It's possible to reach 400 without touching the HM raid but you need like a vault filled with every kind of exotic engrams. I got my warlock from 387 up to 397~ish without doing HM raid. I used this method : Encrypt exotics to raid LL > farm AF for ghosts, artifacts and class items to rais their LL. Rinse and repeat. Not to mention doing NF somewhere during the process.
Also, I kept few engrams as infusion fodder for my other alts to encrypt them as soon as I hit 400 with my warlock. Encrypting exotic engrams at 400 LL guardian guarantees you 400 LL stuff.
Or just wait until Iron Banner.