I personally run my Slann with Becalming Cogitations and Earthing Rod. I then take a Scar-Vet BSB with halberd and Tal of Pres. The reason for Earthing Rod and not making my Slann the BSB is because of a first turn loss on the Honor or Glory scenario when he miscast. But Becalming Cogitations is about as much farther as I would go besides the basic Slann.
I also run a large block of Spears, and they do produce results. Unfortunately, they don't do as much damage as my horde with HW and Shield (but that could be because the Oldblood with Crown of Command is in that one and the BSB Scar-Vet is in the Spears unit.)
I only have one TG unit, and I would agree with Lucas on only taking one large unit. But as you guys have also said, each player has their preference based on experiences and the local opposing armies. I fight mostly Warriors of Chaos in my area, so it's pretty much the Best Core Infantry unit versus the Second Best Core Infantry unit. dk, if you have mostly canon lists in your area, then yeah avoid the Steg. If you fight mostly Chaos and the such as in my area, then I'd run one (if I had one). The skinks are always a good choice for taking out monsters. (After I found out I could slaughter giants and similar things with them, I pretty much said NO to giants in my O&G list.)
Anyway, not a bad looking list. Like I said, I'd just roll with one unit of TG. Up to you.