I expect VP entries to have a tough time in the contest since there are three in the set already.
The main types in Dominion are Action, Treasure, Victory. Curse is its own type too, I suppose, but there is only one Curse card. Reaction is a subtype that can appear on any other type. It can probably be considered its own type, but it has never appeared alone. Attack, Duration, Ruins and Looter are subtypes that have only appeared on Actions. Shelter should probably be considered a subtype, in which case Hovel is as close as we'll get to a "pure" Reaction.
Groves is OK. 2VP for $4 is fairly standard. Trash on buy is fine; in some cases this may even be preferable to Farmland's remodel (maybe you trash a Curse but don't want an Estate). The bonus VP is peculiar and may cause FBI. In a Kingdom with no other trashing, buying Groves to trash Estates is quite strong. An opponent would have to join the Groves race. OTOH, picking up a bunch of Groves means you won't be in as strong a position to buy Provinces.
It looks OK to me.
I somewhat agree with razorborne, but there are other cards that are like this too (Trade Route, Forager, even City).
@razorborne, I think Duke is worded like that because it counts 1:1 with Duchy. Compare:
a) "Worth 1 VP for every 1 Duchy..."
b) "Worth 1 VP per Duchy..."
c) "Worth 2 VP for every 5 differently named cards...."
d) "Worth 2 VP per 5 differently named cards..."
(b) reads better than (a), and (c) reads better than (d). Granted, Duke could have just said "Worth 1 VP for every Duchy" and that would be fine and consistent.