This would normally be our problem. When we finally killed some of the bosses for the first time, we killed them 2-3 mins faster than guilds who killed them 2-3 weeks earlier and often better than their farm times. I often argue about the value of flasking and food buffs when it's wipe night. You can't get Garalon below 60%, it's not because Billy didn't flask and Johnny is missing a food buff or even that the Ele shaman is under-performing.
If a group is consistently getting to the 20% mark and wiping, then I start looking at buffs and dps. If you can't get somewhere consistently, it's most likely not a DPS problem, but a mechanics problem. With maybe the exceptions of fights like Elegon, where you can't get more than 2 orb phases down.