My biggest concern about Chaac is his ability to take the damage, I haven't played too much with this build but Chaac has been the biggest issue so far as we traded very evenly meaning when junglers came to rotate, it was often a 2 vs 1 situation, which can be hard to survive.
I will be the first to say I have only recently started playing this build (about 10 games). However I am having a lot of success with it.
I have found that if i am tank-y enough to stay in lane my teams jungler can focus on helping with mid and duo lane so being able to stay in lane is key to this build.
I know going for Meditation is not normally recommended, but this build is all about surviving without the help of the jungler.
Hide of the Nemean Lion and Breastplate of Valour are there to take on your normal warrior solo characters.
Gengi's can be changed for Pestilence depending on the other teams late game builds.
Frost bound hammer will keep you close and make sure no one gets away from you easily.
Titans bane is late game and should help you do some damage in team fights.
But most importantly Bezerkers shield is a must, once you have it, you can box with anyone and combined with your shield bash you will be able to stay alive and box in lane very easily.
Warriors blessing will be changed for Titans bane for end game.
Second relic depends on how you are doing, if you are the focus of most team fights then i would say bracer to keep you alive, if you are the one starting most fights then i would advise thorns. Both work very well with this build, but I think thorns is just slightly more useful as you can do more damage in team fights.
Focusing on wave clear is essential, hence bludgeon is key early game.
However once you have bezerker shield focusing on shield bash is key for your boxing potential. combined with Nemean, you should be able to win most fights early to mid game.
Scourge is not so important as Bezerker shield is key to keeping you alive.
I started using this build when I was in a game where my jungler wasn't able to help solo much.
Using bludgeon to clear wave then using shield bash to box (with nemean and thorns as well) I have found most people will back off and you will gain instant pressure.
These items should mean you can heal from wave and Meditation is just so useful when fighting in a 2 on 1 situation. But thats what you need to be prepared for, thats why this is such a tanky build.
I haven't used it in ranked yet. But I will update when I know.
Very tanky only need to get mana buff and you should be self sufficient
not many can dash away far enough (once you have frost bound)
can life steal so much the other player will sit under tower
you can take tower hits very well
you will be double or even triple ganked!
you won't do much damage until late game
have to use ult to get out of bad fights (at least you'll stay alive)
you wont do much tower damage
You should be prepared to be ganked a lot, however once you have Nemean you should be able to stick in the fights for a bit longer.
Remember to ward
For early game you will be lonely, mid game you may see your jungler a bit, but you wont be able to rotate until you take tower, which with this build isnt easy.
Late game, rotate and just get stuck in, you can be a great front line, and even better back line chaser, with your ult you should be able to chase the squishies. (but chasing squishies isnt your job, so stay in the main fight). Med will be key to helping everyone else stay in and do the damage while you soak it all up.
If you do find you are the last one in a team fight, remember your wiggles! Wiggles for days and you should be able to do a lot of damage with Nemean and shield bash.