Why So Much Tanky DPS? Starring Aatrox
One of the common complaints I have heard about League of Legends is based on the champions. Many players, especially those with experience in other MOBA games, tend to note whenever a new champion comes out who fits within the meta category of tanky DPS. Champions such as Jarvan, Rengar, Nasus, and the upcoming Aatrox all fit within this category.
The main requirement is them to be both damaging and survivable, enabling them to jump into the middle of a raging teamfight, survive the damage being thrown around for a reasonable amount of time, and themselves throw out a significant amount of punishment on the other team. Some champions fit into this category based on being able to build straight tank (like Jarvan and possible Aatrox) and still be able to do enough damage to be impossible to ignore, but the distinguishing feature of the champions is the combination of survivability and damage.
Many players express disdain for the number of champions who fit this mold, claiming it as toxic to the game's overall environment and stifling on its meta, requiring certain team compositions to function. I, having played several MOBAs in my time, respectfully disagree. Tanky DPS should never be the only champion option available, but there are several very good reasons why it is an important one to have, and Aatrox is perfect to show off the reasons why.
Spread the threat, kill the carry
In many MOBA games, including League of Legends, the teams include carries. These champions are generally ranged champs and focus almost exclusively on damage in their item builds, enabling them to inflict tremendous amounts of punishment once they get built. With the addition of lifestealing mechanics, regaining health from enemies based on the damage they inflict, in many MOBA games these champions become literally unstoppable once they are built.
Tanky DPS are often very strong duelists. They can take severe punishment for several seconds and are often still capable of inflicting enough damage in return to overcome things like lifesteal. Having a champion around who can take punishment but still out-damage those auto-healing mechanics helps prevent hard carries by forcing them to be careful. It makes them pay attention to positioning and rely on their team to peel enemies away from them. Most importantly, it prevents champions like Tryndamere from simply walking into the enemy team, popping cleanse and his ult, and going from one champion to the next as a murder machine. He can be stopped.
Aatrox, as an anti-carry, has a gap closer--a damage steroid to let him burst down a champ who hasn't built any tanky items and a slow to keep them from kiting him. Carries need to beware him as a result. He also does enough damage that the enemy team cannot simply ignore him, regardless of whether he goes after the carry; keeping the game dynamic regardless of which champions are involved in any given fight.
Variety of roles
Champions who benefit from building both tank items and damage items can fill either role as needed. Building both tends to create a strong combatant, but for specific team compositions or to catch an unsuspecting enemy by surprise, many of them can easily build entirely one way or the other.
Aatrox, for example, can opt to build straight tank if the team needs a beefy initiator, jumping into the middle of the enemy team and hitting Massacre and Blood Thirst, and generally acting as a huge distraction while the team's actual damage dealers win the fight. He is also mobile enough to conceivably build as a melee carry, letting him close the gap fast and rip whomever he reaches apart.
Variety of teams
The meta for League of Legends is fairly stable right now. A ranged carry goes with a support champion, a tanky DPS goes to lane alone, another goes to the jungle, and an AP champion goes mid.
Then there are champions who can break that meta. Melee assassins going mid, ranged carries going top, and tanky DPS champions going wherever the team thinks the switch-up will work best.
Aatrox, specifically, could go top or jungle easily. Less in keeping with current meta traditions, he could also go mid against certain opponents and simply operate as a serious lane bully or go bottom as a support doing much the same thing, using is q, e, and w to trade hard with champions not able to handle the close-range brawl. Neither option is something to be undertaken lightly, but both are entirely possible given the flexibility inherent in the champion category.
Look at that support. So heroic!
What people often complain most about with tanky DPS champions is simply how generic many of them feel. "I've seen this before, it's just another _____ clone champion." Many of them do have similar abilities, but it is the combination of those abilities into a full team in each champion's unique way that distinguishes them from each other while still allowing the League of Legends to be competitive and enjoyable.
Don't roll your eyes and discount champions like Aatrox just because they fit into a specific category. It is not the categorization that makes the champion, it is the application of what they can do in any given game's unique circumstances.