So my guild just finished up Heroic BRF and Monday we are going into Mythic Highmaul. We have about 10-15 DPS that can pull an average of 30k+ a few around 40k. The rest are between 20-30k. So my question is what fights in HM/BRF can we reliably do, mind we have already done Kargath.
Generally somewhat hard to say without logs. I don't think it makes much sense to focus on highmaul mythic bosses. I'd start with something easy like oregorger or darmac should be doable when you can kill blackhand.
Damage in mythic fights cannot gauged by the single "dps" metric (except for maybe gruul or oregoregor). In mythic fights what matters is that you have damage in the right places at the right times. Take a look at the top mythic dps parses on warcraftlogs and you will see that dps will vary greatly depending on the fight.