I've ran nothing but the OB/Carnie combo for the duration of 8th edition so far. The Slann is not really my style of play, even though it's very effective. For my army, I have 2 ancient stegadons, one crewed by normal skinks and the other a skink chief with war spear. Having 3 big dinos really makes the opponent think about which one they want to target. And T6 on the Stegs is hard for anybody to overcome. Along with a couple block units of Saurus I've had very good success. Needless to say, magic heavy armies give me fits but if I'm able to make it to their line I usually have good results. I've always kept the OB on the flanks and try to get him and a unit of Saurus to charge at the same time. It works for me, but like I said, the OB/Carnie is my style of play versus the magic heavy Slann list. Just my 2 cents...
Iggy