Looks curiously unbalanced compared to Auger Spree.

Do you mean better than, worse than, or simply stating that the p/t are off? I know it's plus more, minus less, but I more often saw Auger Spree used as removal than pump, so it's a trade off - less removal option, more pump.

I think I meant that it looked odd. You're right that +N/-N effects are almost always used as removal though. For the pump to be a reasonable option the power boost does need to be more than the toughness reduction. (Riot Spikes got used both ways round.)

So this is probably quite reasonable. It looks odd, but I think that's okay; it's going to do precisely what it was designed to do and do it well.