Ooze has been a pretty good inclusion. It has it's awesome matchups (dredge, survival, bug fish), I think it's pretty good against UR xerox (URw not that much because stp), and against some combo decks it's kinda bad.
I'm still not sold on throwing it to the SB to play cards like engineer and ouphe. I haven't had enough opportunity to play engineer. Got to tutor for it twice, once it made a double kill against delver and pyro but a leovold would be probably as good there, and also killed a 1/1 ballista and made my opponent spend resources on his second to kill it. Sounds pretty good against creature decks.
While karn is still pretty dominant (and I expect that to last for quite some time unless it gets B/R) we have to have ouphe MD. It's an awesome target for survival in that matchup, we may get locked out of the game before playing it but if it lands it's pretty awesome.
As said in other topics, there is too much going on. I don't expect us to find a clear answer to those questions too soon. At least I won't, as I'm playing very few games lately compared to last year. Those 3 cards sounds like good 1-ofs for the maindeck.