What Garry said.
No healer= no chance at victory.
Leroy Jenkins dps? Let them die if they want to try to tank & not listen.
Tanks always, always always pull first. As a rule, dps should hang back for a couple of seconds to ensure tank has hate, then jump in. If dps pulls hate -then- it's a tank issue. But If dps runs in too quick or pulls first, you have a crappy dps member.
As a rule, only time anyone other than tank hits an enemy first, it is for CC: sleep or sap , etc
Even then, good communication is in order.
Don't blame yourself... Just get in a good group.