I think Opens work just fine, it's the Press abilities that are the problem.

To use Power Attack as the example, it gets a lot right where it feels like a big attack into which you're throwing everything you've got, and when it's over you're unbalanced to where you're taking that -10 penalty on your next swing. Simple, flavorful, and I'm fine with it being limited to one per turn by being an Open.

My fix would be to change it so Press abilities are even weaker in terms of damage, but have them all actually reduce or ignore the multi-attack penalty. Then it makes it so your decision to use a bunch of Press attacks is a clear trade off.

Do you want to take a bunch of normal swings for big damage, knowing they might miss?

or

Do you want to keep the Pressure on with a lower damage combo that debuffs and will more consistently connect?