We have, of course, seen cards with abilities like these played consistently in competitive play, so its quite possible Pluto will see play as well
Trample Thrun cant be the target of nongreen spells your opponents control or abilities from nongreen sources your opponents control
The most obvious of these factors is the synergy of haste with Saproling Burst, which was known to some as "The Fix." That extra turn almost doubled the strength of the Burst and made it hit for the full 20 damage in only two turns, which would normally mean a kill on turn five, or turn four if backed up by a Blastoderm
It can't hit your own dorks and generally the best answers to your things are not on the back of creatures
Its activated ability, paying 1 life and Blighting 2, forces your opponent to shrink their creatures while you potentially benefit from placing counters on your own
Reanimate - Any graveyard