Well yeah, I can understand that the pressure from a Boomkin's burst can be amazing at some point, but I'm not sure that it will be enough to compete effectively in 5.2, especially with the buffs to DKs, rogues and monks, which have the most counters (save warriors) against warlocks and boomkins. Also with mages basically getting a 30% damage reduc against DoTs, the small perks that LSD2 currently brings will be worth even less.
So although I agree with you that the comp can bring some great damage during burst, the window of opportunity for applying it is so small, and its counters are just too easy.
I mean, a monk could basically negate all of your burst just by using Dampen Harm + Zen Meditation. And rogues are also getting more defensive utilities for their smoke bomb with the 20% dmg reduc (although I don't know how effective that'll be), which makes stacking less punitive when you say catch a dk/monk along with his healer in a single solar beam.