Taunting Elf gets everything else through when you attack a single player, and if you can make it Indestructible, it can do the same turn after turn, taunting blockers and letting you make mad stacks of extra cards
That slime is a lot safer than slimes and oozes in Magic, which are a lot more sinister than our classroom science experiment
Decks in this format usually run lots of fetchlands and other activated abilities to the point that I'd expect Harsh Mentor to do 6+ damage each turn that it's alive, which is good value for a 2-drop
I get it's for the sake of the cycle, so this is an observation and not a criticism, but that might be the most niche text this side of "can't be blocked by Saprolings"
When mana can't solve power issues, your mechanic has a huge problem
in these regions, distributors of the game run tournaments