This game is all about card management. So instead of complaining maybe start using it? Draw 6 cards instead of stratagem. Do a mid turn card draw. Gather all tomes you can have. And then kill rhino in one go. If you are unlucky and don't get enough tomes wait for turn 2. You need ANY tome to wound it if you manage your attacks smart.
Yesterday I saw my opponent trying to kill my Rhino using just dumb luck. He failed miserably, I understand his frustration. But to be honest he didn't prepare to fight my Rhino. Next time I expect him to play well.
And keep in mind that Rhinos require shaken tokens to survive. This means no shaken tokens elsewhere. That hurts me most - Rhinos slow down rest of company going to glory because they consume all shaken tokens.