All of those last between 10 and 15 min when composured.
Having to spend an extra 15 sec prebuffing is not the reason they are behind in the melee department.
The reason BLU is better at melee is they have:
1: The gear
2: Dual Wield 3 + an attack boost without the need of a sub
RDM has:
1: very little melee gear
2: DW3 from sub OR an attack boost from sub.