Nature does have a -RES power. It's only single target and only -18.75%, but for tough targets its available. You also get -50% damage against single targets by combining the toggle debuff with the single target debuff + a nice -regen (150%) and -tohit (-15% base). So while nature debuffs are nowhere near rad debuffs, it's still pretty neat. And all of natures buffs include yourself.
For solo play there are sets that kill faster, but in a team nature really shines. While damage isn't buffed to kinetic levels it's still very solid and the group protection aspect is much better than kinetics. Nature really does nothing "the best", but it has a pretty nice tool kit. Resist buff, regen buff, absorb buff, damage buff, endurance discount, endurance providing life spores and pretty good heals on top.