after beating crota on my 32 warlock mt group was nice enough to let me do it as my 31 and yes you can do hardmode as a 31 i was able to do the whole raid as a 31, the only reason we didnt finish crota was cause everyone was tired, we woke up at 4am to do it. So its possible to bring 31s into the raid, being said though i have maxed ghorn which enabled me to dps crotas shields easily edit: we woke up at 4am to get on xbox, i know it didnt start at 4am in australia