I'd be careful with just tanks in League these days, with every champion having some % hp dmg the tanker you get the more dmg your enemies will do, so take that with a grain of salt. League is also getting shorter and shorter with 1 sided stumps so farming up for 1-2 tank items to do what you intend(tank) you could very well be digging yourself in a hole.
Honestly a powerful pick can be flexed also. Sustain with W without needing to auto attack or life steal anything, just walk around spamming W, slow and powerful Q and a reliable engage E with a fantastic ult to boot. The ult needs some practice but overall a solid pick. -( Will most likely get nerfed here soon )
Why tank when you can just sit back like a ADC and just do dmg constantly at top vs melee enemies. Can be flexed more so than Gragas, "kinda even" -( Will most likely get nerfed also tho )
So underrated in my opinion. His sustain is crazy good and his ability to steal his opponents' resources is something people seem to forget when they see a low HP Trundle whenever they 1v1 him. His ult is pretty much an ignite+ death fire touch - it melts people tick by tick.
Can't go wrong with other champions tho, I will say these are bait champions, meaning you pick them at your own safety and a possible L incoming depending on the situation.
A strong laner, tanks does % hp dmg(I talked about it earlier) but his ult is kinda bad in my opinion, not to mention in League these days with as many stuns, slows, perma stuns, taunts, fears etc 1 click and your ult is gone. You're also letting your team think they can troll and act stupid because you're Shen so you're pretty much going to be on babysitting duty the whole game.
Jax is great at 1v1 and a decent teamfighter but his main strength is split-pushing and depending on elo it's something people don't understand in certain elo's. In B-S people expect a 5v5 aram from min 30-end and it's kinda useless for Jax. Unless the enemy team are baboons and you flash Q-E for a decent stun/s he's just a sitting duck and not using his ability to it's maximum that it could be. So if your team gets beat or 1 person dies expect ???????????????????????????????????????????????????????????????????? the rest of the game.