There literally are no cons about this suggestion. (Other than a little bit of time to create the room/mobs/scripts) All in all, this would benefit all players new and old. If you're a veteran player but you took a long break, just stop by the spam test room to get your A-game back and then get out there and kick some butt. If you're new and you want to test how good you are with spams, same thing (just maybe without the kicking butt part lol).. I also would recommend that instead of your idea of plant mob with lots of hp and only takes 1dmg per hit, do something more on the lines of a realistic pvp type mob with average demi-human reductions so that you can test your damage while your at it and maybe be able to make a few tweaks to your build. All things to take into consideration, but overall this is an idea for spam testing mainly, not damage testing. :)