Never take him support, he just doesn't fill the role as he needs items to be effective.
Top is by far the best, just because it's an isolated lane and he has a very good escape manoeuvre in his E>Q, and he fits the meta of tanky dps there.
And yes, he is in fact a tank. Build him as such. The only AD you should be getting is Frozen Mallet, Atma's, maybe Maw, that's it.
lolwut? Needs items? Your passive scales with enemy hp Your shield scales with enemy amount You get free stats Standart gives vision, blocks skillshots (requies timing and precision to do so) and can be teleported on Your spear is also utility + arpen Ult has high base damage + utility
Jarvan support is like Leona+Taric. Simply godlike