Will see what I can suggest here soon once I finish washing the dishes. Commenting so I can find the thread again in case I lose it.
I can only speak really to Ornn top.
So, Ornn is actually a fairly strong tank in terms of what he brings to teamfights and his current laning. The right item buys can help sustain you greatly. Late game, his masterwork items can be really powerful on both you and your allies.
Ok, so browsing back through your matches, since that’s usually the best place to start. First point I’ll mention, I don’t recommend both Randuin’s and Thornmail. They both have Cold Steel, and as far as armor/health value, a Sunfire/FOrgefire Cape would be better over Randuin’s. Only downside is losing the crit damage reduction. But getting two Masterworks can make a big difference, especially with the coming buffs to Forgefire Cape, Infernal Mask, and Frozen Fist.
For the most part, builds are fairly sound. Probably once you had Abyssal against Kayle, I might’ve considered a Warden’s Mail for the Attack Speed slow, plus she does still deal some physical with her autos.
A lot of tank Ornn, though, is getting used to how his kit feels. It is a bit more clunky, but landing the skills feels worth it. Getting used to the Q-E combo takes some practice, as well as using E so it hits terrain. I recommend continuing to practice it though. Personal preference, Maxing E over W, in my opinion, feels pretty good, it lowers the CD of your core CC ability, it scales with your resists, and it’s base damage is pretty good for quick waveclear. A W-E for me as I get more levels in E will often clear the casters and take the melees low if not kill them until later in the game. Just be wary of pushing too hard and overextending.
Runes, results may vary, but I based mine off a top Ornn player, running Aftershock, Demolish, choose between Conditioning/Second Wind/Bone Plating depending on match-up, and Overgrowth primary, then secondary is Minion Dematerializer and Cosmic Insight. Stat shards I often run Adaptive Force, then resists depending on my match up.
Beyond that, a lot comes to practice and getting a feel for the kit, as His timings take some getting used to. But when used to him, he can fare pretty well.