Defensive Roy doesn't work that well in most Matchups. Against certain Floaties like Kirby you want to play defensively because Kirby can combo you pretty well. Sonic is also one of those MUs where you really can't overstep your ground because he has too many safe things such as an auto-cancel dair, a bread and butter that is safe (side-b), an up-b that prevents you from juggling. Yeah pretty dumb to have given him a buff that just makes his approach down more safe. Sakurai please -.-(Btw it's even worse now with this freaking shield patch, it would have actually been a good patch if they didn't patch customs at the same time smh)
Anyways it's not really that efficient anyways, Roy has so many good strings and follow-ups that just sitting behind is pointless unless you're looking to confuse your opponent. But if you do play him defensively you'll be surprised to know he is much better than Marth at it. No surprise there anyways.