While there's a bigger danger to wraths that looms over a wide board of humans, giving them an ounce of spell protection and power boost is pretty incredible for the rate of mana you put into the Vanguard
It is still the hand in either case
So, to some extent, Koth is an incentive to go Mono-Red or close to it, and if you can do that, obviously the -3 will kill most stuff, but on a board that is built out at all, your opponent can still easily deal with Koth This will be able to attack with higher power a decent chunk of the time for sure, but the times where it is just a lowly 2/3 will feel pretty rough
None of these really tie in with the Elven Council theme unless its meant to portray the Elves as an all-compassing, inclusive tribe
However, this power doesnt come without a cost, as youll be required to pay the creatures CMC alongside an extra green pip of mana