the problem here is fluffwise slanns should be at least lv8, know unique catastrophic spells, be loremaster (everything but racial lores) and so on, but it would be game breaking. I feel like slanns with the old armybook were a good compromise between the background and the gaming table: they could cripple an enemy caster (like stated in the fluff), generate more power dices giving them magic supremacy (like it should be) and master a single lore after thousands of years of study, practice and instinct (they are uber-intelligent and incredibly old creatures made to be the best casters in the world, i think loremaster is a must). Ok, it was a problem always being able to 6 dice an uber spell and dodge the miscast with cupped hands, but remove cupped hands and it was quite tollerable, unless you were using life. Moreover, we all know slanns purpose was buffing our troops against enemy deathstars (and if they think making TG cost 14 pts instead of 16 could fix it, they must be quite stupid)
Anyway, i hope our slanns will get a buff when (if) the end times arrive for us. Even better if we get spawnings, a big flying monster and/or something else