Generally speaking, nobody around here touches Lash of Submission, because enough of us are utterly nuts enough to have sharp objects in the trunk of our cars. :p But more seriously, it's just dumb, so we don't mess with it. If somebody does bring it, it's an out-of-towner at a tournament and we just bitch about him later and laugh about him not getting any of the prizes since we weigh sportsmanship and painting as high as winning games.
HOWEVER, that's not really what you asked, now is it?
If push came to shove, and I had to deal with Lash of Submission on a regular basis, I'd just make it a point to have something that can whomp a daemon prince in every squad-- usually, that means a power fist. As a matter of habit, I do that anyway, but even an assault-happy monster is going to get seriously mauled by Sergeant Anonymous' power fist. Sure, you'll lose five or six Marines before you bring the prince down, but whatever-- you're still probably on the better end of that deal.
Another alternative is to get creative with your transport vehicles. I use 'em to block heavy weapons squads' line of sight once they're empty, since even if they blow the thing up, it's still blocking line of sight, and if they don't bother blowing it up and instead try to move around it, you can just park the vehicle in front of them again until they do bother blowing it up. Just do the same thing to whoever's casting Lash. It requires line of sight, after all. If the only thing the caster can see is an empty transport vehicle (or two, since sometimes it takes two to completely block useful LOS for a big model like a daemon prince) then that Lash isn't terribly exciting.
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