I love the idea of having 2 slann in my list. I would roll with one light and the other life, both with the loremaster, immune to non-magic, and extra power dice disciplines. I think i would give a TG unit to the life slann because of the throne of vines spell makes wiping out the TG unit with a bad miscast less likely. SO the only BAD side i can see to this is that power dice are going to be in shot supply, especially if i get bad rolls, and the two slann, outfitted as mentioned, exactly fills up the entire lord section in a 3k list, so i cant do some awesome oldblood stuff. Thoughts and ideas?
If you run a life slann and are worried about power dice, make sure to grab the forbidden rod. The life slann can just take the wounds from the forbidden rod and get them back by casting more spells. I believe that 2 slann can work at 3k. I'd say try it out.
I tend to think that 3k is a bit too few points to take 2 slann. However, if you do there may be a more optimum mix of items/disciplines to take. If you put one of the slann into a TG unit then you can replace its ethereal discipline with either the ignore 6s discipline or cupped hands, probably on the other solo/light slann. If you swap out for cupped hands then the 6+ ward against war machines pays for itself over time even if only half your opponents take war machines. As you have 2 slann power dice should not be a major issue as you can attempt to cast with fewer dice as failing to cast with one allows you to continue the phase with the other so you can make casting attempts with fewer dice. This also increases the net effect of your bonus dice. If you play with closed lists and your opponent knows about the ethereal discipline, consider not taking it even on the solo slann as you opponent may assume it isn't present and not try to attack it with mundane weapons. Even if he spots it, as long as you are close enough to the life slann you should be able to survive all but the most intense attacks as you also get the reduced look out sir if close enough to an infantry unit.
If you run 1 Life Slann and 1 Death Slann the Death Slann generates power dice for every wound he causes as the Death Lore attribute, so theoretically he can feed power dice to your Life Slann while also eating up you opponents dispel dice.