I run Obstinate Baloth as a more "fair" Thragtusk, but the discard clause is strictly trinket text - I'm all about the life gain (and even there, it's barely holding its spot). Loxodon Smiter, on the other hand, is an undercosted beater as a 4/4 for 3, which sounds kinda good - however, that it's multicolour really downgrades it to just "okay". Unless your format is dominated by Grey Ogres, Smiter is gonna be extremely narrow and not a very juicy pick.
IMHO (and a lot of this is thanks to Jason's philosophy on multicolour cards you've probably seen in some of his articles), you have to consider that multicolour cards only really go in an extreme minority of decks ( ones), so, in a typical environ, your multicolour cards need to be really fun, really powerful, and/or extra spicy. In all three of these regards, Loxodon Smiter only really has the potential to be valuable as "really powerful", but again, to make it really count as "really powerful", your format's going rate on 3-drops should be about 2/2 vanilla for a 4/4 that's two colours to do anything more than wheel forever until it gets to a player as a boring, but undercosted, beatstick.
IMHO (and a lot of this is thanks to Jason's philosophy on multicolour cards you've probably seen in some of his articles), you have to consider that multicolour cards only really go in an extreme minority of decks ( ones), so, in a typical environ, your multicolour cards need to be really fun, really powerful, and/or extra spicy. In all three of these regards, Loxodon Smiter only really has the potential to be valuable as "really powerful", but again, to make it really count as "really powerful", your format's going rate on 3-drops should be about 2/2 vanilla for a 4/4 that's two colours to do anything more than wheel forever until it gets to a player as a boring, but undercosted, beatstick.