I suppose you could have known that running the laser from 2 lithium cells wansnt going to work all that well. During discharge 2 cells provide about 7.2-7.4 volts, and with 2.55 lost between the driver and reference this will not power a high powered bluray reliably.
I bought a number of BW512Ls from that Hank fellow who was shutting down shop a while ago.
This diode was not one of the ones I bought from him - but I'm still going to start playing with those over Christmas, and see what I can push them to with 700mA of current.