This is a summary of talking to many top players in different versions of the game (International/China/Korea). If you are not a big spender be sure to spend your resources on the right heroes for late game! Always be farming shards, don't waste stamina on gear alone! A hero can go from low tier to top tier in a single patch, if you played any card collecting games like Puzzles and Dragons, Hearthstone etc you know how quickly the landscape can change. Characters are ranked based on their overall value on an end game roster.
Tanks:
Admiral - The first hero you get in the game becomes one of the best, if not the best tank in the game once you complete her legendary quest. Great combination of armor, magic resistance, and dodge, very useful passive, one of the highest health pools with her legendary skill. Her INT is higher than all physical characters in the game if you plan your enchants against arcane sapper, her aura is great for chaplain if you plan to run a 4 healer team or leave shadow who is good in every line-up. Best of all, you don't have to farm for her soul stones, you can get her to 5 star with pure bronze chest pulls by the time you are 90, making her a super cost effective character. ****1/2
Brute - A dominant tank in the early game and unfortunately can not keep up once Admiral/Shallow Keeper reach equal stars. His durability is on-par with Admiral and Shallow Keeper in late game, but his ultimate is very weak against mirror images. His damage output is mediocre at best and it is much, much harder to get him to 5 stars while you can get Admiral and Shallow Keeper to 5 stars with bronze chest alone. He does come with a high damage DOT for Outland portal. His legendary skill gives 180 strength to all other axe users but at end of the day, there is very little incentive to farm for Brute when you have Admiral, Shallow Keeper in late game. **
Drunken Master - A dominant 73-87 hero who starts to struggle in late game. He offers no protection against arcane sapper, his ultimate is easily interrupted, and his magic resistance is a problem at level 90. If you already invested in him heavily, slow down and wait for a legendary quest down the road. Still useful for Outland portal against Phoenix. At level 90, arena fights are much longer, you need pure defensive tanks. Panda's orange gear is too much damage and not enough durability. His drunken haze is still a huge asset against physical teams however, especially when combined with other blinding effects. But more often than not Drunken Master will find himself on the bench at 90 against tanks with legendary quests. ***1/2
Ironhoof - Incredible opening move blocking all of the opening damage and crowd control from the other team, some of the best defensive stats, just a great tank throughout the game and unlike Admiral, doesn't need end game gear to be good. His ultimate can be a double edged sword in arena fights however and put your own team in bad spots. And more importantly, he is much more expensive to acquire than the Admiral. His yet to be revealed legendary quest may put him over the top down the road however. It is pretty scary how competitive he is without a legendary quest. ****
Psychopath - The highest INT tank in the game, with an amazing legendary skill that greatly improves his rotation. Plan your enchants carefully and he can have higher INT than most of your casters to shield against arcane sapper. While he doesn't have as much dodge as theAdmiral , he more than makes up for it with a DOT and burst magic damage, covering 2 of the 5 Outland portals. Because of the way his specials are all luck based, you can beat contents that you otherwise have no business of beating with repeated tries. Unfortunately the international version of the game is without the legendary equipment refactoring feature in Chinese version of the game, and he is missing the critical 20 dodge (unlocked when you add 100 agility to his legendary gear) for tanking. As a result he can not solo tank physical teams and really needs another tank or arcane sapper to take some hits for him. ****.
Savage One - As a damage tank he is behind both warchief and panda in effectiveness, but he has the best armor debuff in the game and ensures your success in every raid fight that allows physical damage. His overall value really depends on whether you are in a place to top damage meters to begin with. If you consistently finish in top 10 he can push you over the top and reap the benefit of high guild coins. His awakening ability adds 180 agility to all naga heroes (deep voice and vengeance spirit), coupled with the huge stats increase from legendary gear, makes him a serviceable tank for grand arena. Against single tanks or even arcane sapper on offense, you may be able to surprise them with a quick armor debuff and burst physical damage. ****
Shallow Keeper - More armor (significantly more once he gets his legendary quest), less damage, less dodge than the admiral. Low INT makes it much harder to hide other characters like commando from arcane sapper when he is the tank. The Admiral is better than him overall but they are interchangeable in many line ups. Admiral is cheaper to get however since you start invest in her from day one, and I rather get Warchief, Panda or Savage One instead of another defensive tank. ***1/2
Vanguard Warrior - Useless outside of arena, one of the most expensive heroes to gaer up, but vanguard warrior and ember blade have been one of the most popular duos among top finishers at a recent Chinese national tournament. Ember blade starts off the match as a tank and takes a few hits for faster ultimate, vanguard warrior charges in, get their whole team into a clump and ember blade does his massive aoe damage. This team almost always has a silencer who will drain entire enemy team's energy since they are clumped together. And old curse, phoenix and succubus are usually added in for additional aoe damage in the final two slots. Both vanguard warrior and ember blade are vip11 heroes in China, making it a pay-to-win team. It is amazing a team this good is available to low paying players here. ****
Warchief - Struggles against Panda most of the game but finally becomes better than Panda at level 87, his orange gear is defensive instead of damage, coupled with high life steal, he is really strong very strong from 87-89 and even early 90's until other tanks get their 6th piece of gear and legendary ability. Resurrection is amazing in many situations, especially in the new grand challenge mode where he is the only tank with two lives every fight. Still, low health pool makes him much more vulnerable to interrupts from damage, and outside of against mirror images from cloud walker and double tanks for him to leech health from, he is squishy. ****
Warrior Monk - I really wanted to love this hero. Two stuns, full screen AOE stun, what is not to like? Problem is his skills are all magic and not only they are vulnerable to silence, he also gets a ton of spell caster gear as a result of it, as a result even with orange gear he is on the fragile side. As an INT tank, Psychopath is just better in every way. Better defensive stats, much higher INT, lucky burst damage can win matches by himself, and cheaper to farm and gear up. He can do well against double tank teams or when paired with an offensive tank like Panda, but in the end just doesn't bring enough to the table to be a priority. His legendary quest boosts his health as well as other beast heroes, you will still get more mileage out of Admiral and Psychopath. ***