1. Terrible grabs take them out of block for no cost to you, even though they should be buffed. You could also just wait blocking yourself for a few seconds and the AI will literally always come after you. They never sit there and block for more than a few seconds, if that.
Valentine charge attack can be interrupted, but is not likely at all to be stopped if the enemy is actually blocking.
2. If this was about certain characters needing buffs to their grabs then I agree. It's been talked about earlier, so I'm certain the devs are aware. I disagree with making blocking even more punishable by adding in a mechanic that only lets you play defensively for any short amount of time. If you're good, you shouldn't be blocking for more than a second or two to tank an attack anyways. And that's only if you don't kite them like you can.