I am utterly convinced that 3 squads if blasterborn are godawful and a complete waste of your elite slots. Having a single squad is fine, they are only a small element of the larger army - once you start investing huge amounts of your anti-tank fire into blasters though things can go wrong very, very easily. The only reason it even works is because blasterborn are normally backed by warriors in venoms so you do literally drown the enemy in light hulls. This still ignores the fact that DE infantry really aren't going to take anything at 5 strong, so you get completely screwed by certain units if you cannot stop them - i've seen a variant of the green tide at 1500 dismantle a venom spam army simply because the venoms couldn't get enough wounds on the boyz AND their supporting fire before the sheer numbers proved their worth.
Even then it just smacks of stupid list design because the internet thinks spam works - here's a hint: it doesn't unless you play silly points. Blasterborn have their place, but building an army out of them isn't the way to do it (i've seen some interesting things happen with trueborn armed with shredders and maybe splintercannon depending on points).