Yea that's why you need to have great MA to force a h2h exchange. And definitely an ability to get up into the air since that's where opponents will flee to from your decay.Well but it's quite circumstantial. If you can't rust the surrounding floor to get someone then you have to go with the good ol touchy touchy.
I'd probably definitely want Rokushiki as one of my MAs for that. D
And maybe Hasshoken. Wonder if you could combine Hasshoken with the decay fruit for decay shockwaves. Disintegrating everything in your path.