actually you can tank him with all viable raidspeccs, it´s just most important that you are at
365 FR and that you have a large healthpool. Be soulstoned all the time cause even I, after we have done leo at least 15 times get blown away every now and then.
Soul link will just take the sting, from his really large crits, so if you haven´t got a large healthpool (13k+) you should considder a SL-specc.
Remember even though you need 365FR you
have a decent +spellhit value.
Would that not be the perfect time to try a raid-demo-specc? that way you are perfectly fine set for both heavy damage and tanking encounters like Leotheras and Capernian.