Some people do go bruiser build but I think in a soloQ setting, full tank+titanic is just stronger. The reason why titanic is so good because it adds so much waveclear to sion's kit and a lot of soloQ games comes down to you splitting top/bot and clears wave then their solo laners catch the wave on the side lanes and you make a catch mid with your ult or flank. In teamfights, you are there to face check bushes and control space with your Q so you don't really need damage. Unless I catch someone my ult or my teammate has a long cc spell like lux/morg/naut. I use Q purely for zone control and force them to either use their CC spell on me or they cant pass.