The nastiest units in that army are his Swordmasters and Dragon Princes. The Dragon Princes won't be that much of a threat if they are split up in units that are only 5. They dont have a rank bonus, and generally just taking out one of them will screw up his unit. The trick with those is not letting him charge your important blocks, especially not in the flank or rear (even though he needs more ranks to disrupt, but still). They have a nasty 10-11 Str 5 attacks ASF with rerolls. Those will hurt if he charged a unit not prepared. You can vastly decrease their potential by either getting ranged/magic to pick a few off OR buffing a unit and making him charge that unit. Str 5 won't do any good against Toughness 8
The Swordmasters are pretty nasty. Try to target them with magic AND salamanders. They die easily under flame templates
Beware of the shooting power of his seaguard. He might set them up in units like 10 wide with 2 ranks and when you start getting close reform to 4x5 and voila you have a worthy combat unit. But meanwhile you have a constant firing of 20 shots into a unit. If he has 2 or 3 units like that all targetting the same lets say Saurus unit, you won't keep them all alive.
Basically try to get your Saurus units in combat asap, they will absolutely destroy anything but Swordmasters, White lions and Phoenix guard.
In my opinion Light and Life are the best lores to pick on your slann. Life has the ability to buff your troops AND kill half a block of those seaguard (The Dwellers Below). Light gives you the ability to move faster(so get your saurus in combat faster) and override their ASF if I'm not mistaken? I usually go with life because it opens up a slot for a different arcane item than Cupped Hands. My slann usually has Lore of Life with Bane head and Feedback Scroll to kill off a lvl 4 mage. Really Useful.
And last but not least: Skirmishers. Try getting some skink skirmishers. They are excellent to soften up some units and just generally annoying your opponent.
For instance if you have a good 10 skink sirmishers between a block of his spearman and a block of your warruiors, just let them charge the skinks, do a stand and shoot if possible and then hope that your skinks get overrun. He then charges onto a block of your saurus. It doesn't matter if he charged you, he barely gets any benefits from it. A good block of saurus warriors can easily take the hits of a charging unit like that. But usually High elf players dont fall for it. Don't do it if its a unit of White lions instead of spearmen/seaguard
I hope this was helpful if you have more questions just ask!
edited: fixed some typos probably more in there but meh
