Karthus Support
I don't know why people consider 
to be so weak in a supporting role, his wall is great for zoning off opponents, it takes a reasonable amount of skill to use his Q which is an absolutely brilliant harass tool from the brush. His ult with 
and 
and 
is just insane on squishy targets like the ADC (which every team comp has). Plus if you save him as last pick in champ select and select another mid-laner, people will usually take assassin or squishy junglers like 
making him a perfect pick to provide powerful kill pressure while his Q, W and E are useful in helping your ADC get fed. Does nobody else play him as a support, for me, he is the perfect example of a support that can be a threat by themselves and provide support both in and out of death.
He does take fair amount of skill and practice to use, especially in using the ult when its going to be more effective to both your lane and the mid and top lanes as well. Karthus Support is all about timing and having good zone control which makes him a really viable support imo.
I suppose people pick 
, 
, 
and 
because they are much easier champs that will usually guarantee the BIG PLAYS that the LCS craves. Mages have never been popular compared to big bursty assassins or tank bruiser champs. 
is not a mage by the way, not with her rediculous mobility and ultimate that she can spam 3 times. Could you imagine if 
could spam her ultimate 3 times?
and
). He cannot peel, he cannot heal, and his base damage is not high enough to be worth anything without a significant item advantage.
