Is there a compelling design reason to go off-color?
There might be, but I think it opens up some interesting space.
This could be played in a deck with 0 mountains, for eg.
Also it keeps both the bestow and mana costs low if I can't gaurentee a given deck can cast both halves of the card. Were the whole card red the bestow cost might have to go to
or
for safety reasons, which would probably make it horrible.
Lol tension. I think I would always play it as a creature if I needed a two drop and it wasn't already outclassed on the board considering what was in my hand and always bestow it in any other situation.
So, like any other bestow card?
It's actually kinda interesting the mechanical space theros creates using these two mechanics. Bestow incentivises you to cast the creatures early only if you have to, with the promise of extreme value later on. Monstrosity says to cast all the creatures super early, because no matter what happens you'll have some value later on.
Sometimes I don't give WotC enough credit