Seeing Teclis on the board tells you something about the game about to happen. Playing HE is an uphill battle for many armies, and this characther is akin to rubbing salt in wounds. That and making 2-4 hours potentially not fun at all.An Elf Magic Army should have Teclis. Take Teclis. Always take Teclis. He is a monster mage, and ignoring the 1st miscast each turn, plus his extra dice make him a MUST.
High elves are challenging enough, and there's limitless combination to explore and have fun with if you're a HE general.
Heck, I don't even use slugtounge all the time, just because I'm worried about friendly matches. And sluggy is not even 1/4th as powerful.