Yeah, the fact that I'm not actually clicking shit for the first however many minutes is a big plus for this game.
Other than that, my constructive criticisms would be:
In most games of this nature that I've played, rebirths come fairly quickly at first. Like, within an hour or two at most of your first finding the game, it is more beneficial to rebirth than to grind it out longer. Subsequent rebirths can take longer, but not too drastically. I know this because I always fucking wait too long. In your game, I had no chance to rebirth until over a day into it (granted, it ran minimized most of the time so I was missing out on arena stuff, chests, etc. but still, it wouldn't have changed the time by a factor of 10 or so like I'm used to).
Also, the higher tiers take much, much longer to get to than seems normal. I realize it is a balancing act between making them too fast vs not having enough tiers to keep it fresh, so you'd need to create several/many more tiers if you sped the progression up, particularly if you also sped up rebirths as I suggested, so that might be more work than you are looking to put into it.
Finally, is there ANY way to fix the browser issue? I realize that's not your problem per se, and people playing at work isn't your problem either, but I have to keep it minimized 99% of the time, so I never progress very far in the arena. I even left it up last night when I went home, but since I locked the computer apparently that counted as "not visible" so I am back down to Arena 50'ish. Can it be made into an app or something? That would limit your metrics I'm sure, but it would eliminate the problem.
Either way, I think it is a great effort and I appreciate the change-ups from typical idle games. Not sure how much you value your time or the sales you might get, but this would be an automatic buy for a lot of people at 99 cents with a few upgrades. I'd imagine you could get a few thousand sales easily with a little promotion, but I'm no expert either. Good luck!