New Grasp is a very strong, healthy concept, but with how potent it is in an extended fight, it should lose the ability to keep it stacked/keep it ready to proc while you're fighting minions or monsters. Because now, in addition to the current issue, where someone like Ornn would have a fat chunk of damage always ready if you ever try to make an aggressive play (and thus guaranteeing you're going to lose the initial trade and have to commit to a longer one to even it out) -- the new Grasp users, like Darius, will also do that, but then they'll also get anywhere from a little AD to a very scary amount of AD, so engaging in a long trade with them is now also a bad idea -- you can't disengage and then wait out their Grasp, especially Darius, who doesn't even need to hard-shove his wave to keep it permanently ready. It will promote a very non-interactive style of play where once someone gets a proc or two, your only winning move is to just avoid them, because they're really only going to lose the stacks when they leave their lane.
Basically, if Grasp keeps the combat with minions letting you keep your stacks, it will discourage almost any form of trading whatsoever, because you'll lose both in the short trade and in the long fight. Remove it, and you get rid of the only problem Grasp has.