Crusty Old Meatwad (he/him)
I don't think it's reasonable, and I think it more and more. People have lots of ways to gain Combat Advantage without using Stealth. 13 other ways, in fact. Asking the Rogue to break LOS completely before allowing another Stealth check (under cover or concealment then) isn't unreasonable, IMO.
Everyone keeps focusing on the rogue.
It's not just about the rogue. A ranger attacking at distance with stealth as a skill will often want to gain combat advantage from it, to offset the cover bonus he is granting his foe by placing himself behind cover to begin with. Your view would make cover a net harm to the Ranger's attacks on a fairly regular basis.