What sort of magic support is he running?
Personally I would stick with the original list you had in the first post and run Life or Light on the Slann. If the magic is tough grab Becalming Cogitation, otherwise Rumination + Mystery are fine. Life is a solid investment, but I would highly suggest switching out to Light as it has a number of utility spells right from the get go.
Send your Skinks and Terradons after the Eagles first if possible, then the Swordmasters as suggested. The RBTs can be a pain but if you pick up the Sun Standard on the Temple Guard and screen your line with skirmishers you should be able to mitigate the worst of it. They shouldn't cause your rank and file too much hassle - but they'll ruin your Salamanders if given the chance. Bubble Pha's is helpful here.
Your Saurus should be able to handle his core, whilst another unit can distract the White Lions or Swordmasters whilst you Dwellers/Banishment or poison them off, respectively. Run one Scar-Vet on a Cold One with Dawn Stone, Dragonhelm and a 15 point item of your choosing (I recommend Golden Sigil Sword to negate those dastardly re-rolls or at very least a potion of Speed). Give him an additional hand weapon if he doesn't have a magic one, and watch him rack up the CR. Just watch out for those RBTs. The other Scar-Vet can go on foot to give one of the Saurus even more punch: Amour of Destiny and XHW has a nice balance between killiness and toughness, or ASF sword and Glittering Scales is particularly infuriating for High Elves as it strips them of their re-rolls and makes your Scar-Vet harder to hit.
Buffed by Light or Life, your Temple Guard should be able to match the White Lions - especially if you have been able to whittle them away with magic prior to this. Don't go crazy like 6-dicing Dwellers every turn, but keep up the pressure. You can do some fun things with the Champion too - with the Terrifying Mask the unit causes Terror, which means anything they charge might run away, and also Fear, which means anything they fight might end up WS1. May not seem like much, but the more Leadership rolls you force someone to make sooner or later they will fail. Baring in mind that the While Lions are Stubborn and will pass their unmodified LD8 most of the time, you want him rolling a lot.
If you can, try to hold back a unit of skirmishers just in case you need to redirect the White Lions at a critical point, rather than needlessly engage them. If you can squeeze in some 50 point Skink Javelin units to do this as well, all the better.
Skorxigor aren't really worthwhile unless he is running either cavalry or chariots. Don't worry about Spears - you want the 6+ ward over a handful of additional attacks.
As far as deployment are concerned, here's some tips: start with the Terradons in one corner, then Skinks on the other end of the battle, then skinks back towards the Terradons, then Salamanders behind terrain. All of these units have high movement and maneuverability, so they can quickly reposition after turn one.
Remember that Elves are all mouth: they can't get anywhere near as much as they give. Weather their attacks and you can smash them with whatever you have left. If you are running Life then your priority spells should be Throne, Flesh to Stone and Earthblood: everything else, including Dwellers and Regrowth, should just be used to draw out dispel dice. Try leading with Shield of Thorns because it can be cast into combat and will do damage before the Elves attack. A canny opponent will, of course, know to block Throne which is why, amongst other reasons, I suggest Light: Speed of Light is both a buff (easier for you to hit) and a debuff (harder to hit, no re-rolls against I10); Timewarp can give you a surprise charge, a bonus attack and strips ASF, and Pha's is a handy cheap buff (and the bubble version handy against mass ranged fire, as mentioned). These three should be your priority spells: Banishment and Net are good threateners, and even Burning Gaze will ruin an Elf's day (the long range version is especially useful against RBTs and Eagles alike!)
Edit: Did I mention Net? Net is awesome. Net the Swordmasters - spend another turn shooting them. Profit!
Whatever happens, take notes (pictures if possible!) so that we can see how it turns out!
