Well, first:
You want to keep in mind game-length for builds.
You also want to keep in mind when you're power spikes are on a given champion.
And finally, you want to organize your builds in such a way that the component items don't set you back when you need power.
Average game length is ~33 minutes, and more importantly for build paths: average income is almost exactly 11,000 gold.
Due to consumables (and a lot of that being in your bank when a Nexus explodes), you're probably only going to work with ~10,000 gold in an average game. With most boosts having a 1,000 gold price-tag, you're looking at 3 major 3k items.
For optimization: it's also worth considering several 3k items don't offer their unique passives mid-build, setting them back to a fully completed item: which you won't have access to until a single battle if that happens to be your 3rd major item.
As how to build:
Tanks are pretty much never late-game carries, and even ones that are are almost completely reliant on being tanky enough to do their job, rather than having range or mobility to do their job. If you take a big hit in durability early for better scaling late, you might never see your late game.
Basically - you don't want to rely on Warmogs and Thornmail together for your armor and HP, as you'll have no armor for a good portion of the game.
With a tank - you usually want items with both HP and armor or MR. More the Trinity Force path in defense - where Sunfire Cape, Omen, and Spirit Visage really shine.
%damage reduction also scales the power of HP. If you have 2000 HP and 0 armor, you have an effective 2000 HP and can take 2000 damage before dying. If you have 1000 HP and 100 armor (50% DR), you have an effective 2000 HP and can take 2000 physical damage before dying.
Lastly, scaling 2 stats together is pretty much always better than stacking a single stat within LoL: If you have 1500 HP and 50 armor (33% DR), you get an effective 2250 HP vs. physical damage.
So, don't grab Warmog's because Cinder Hulk synergy. Armor and MR scale with HP better than actual HP, and you can get the best of both worlds with Omen, Sunfire, Visage, and Veil (you're build seems to heavily suffer from HP stacking at all costs with 3 nothing but HPs items).
Anyways, I'd probablly run with:
As a best tank build.
If you're tanky DPS, focusing more on AoE damage and self-sustain than team-wide defense.