Why do they allow exp suckers in games? I understand "quick match stomping, but I don’t get the real reason. They don’t contribute to high level play, so why do these heroes exist in the game?
Side note, I want to join quick match and have fun. These heroes make ranked more fun. It’s a one or the other, and frankly, if I am playing this game I shouldn’t have to choose.
Smells like a… potatoe… 
What is a “RTS” hero? Real time strategy? So Abathur or macro heroes like Azmodan who spawn minions on separate lanes at once? Illusion Samuro?
I can assure you all of them are played at a high level (azmo is not that popular though), in fact they are contested picks at the highest levels.
Soaking multiple lanes at once or split pushing is still as valid as strategy as it ever was. The game isn’t just about mindless teamfights. Whatever kills the enemy core works. Even flying there with a Medivac once keeps are down.
It is true what MetalDtector is saying, the Medivac strat was at one point a huge problem.
There also was a time where Leorics just stood at the enemy towers and attacked them til he died, he then respawned at the towers and kept going until he was at the core, the rest of his team only had to push lanes when empty(When they ran to deal with Leoric) or Def them when the enemy realized they had to race him.
We have also seen a number of AFK pushers top, but that has been heavily fixed now, nowadays everyhero is nearly forced to join in at somepoint.
I would also like to jump on the “RTS?” train here.
Not sure how that term would work in HOTS. (Would love to see a Peon hero though).
You bring up a really important point! If you look at all the types of heroes from dota to league to hots, etc, theres’ a handful of playstyles that appeal to different people with different strengths. Some of us one-trick and others prefer to hop around to what feels fun that day.
Mobas are generally action packed and the initial “brawl” at the start of each match lets each team test each other. Its a rumble and its fun to just go at it.
So to your point, where do “exp suckers” fit in? I’m no game developer but I would imagine there’s a handful of reasons including variety and appealing to a larger audience than just the classic "hypercarry, support, tank, flex, flex, " which might get a bit stale. It’s almost like you’re playing an rts and seeing if the invading forces can score a kill or if you can trade up. You took down a few towers, took more exp, managed resources better and now the ganker has to demonstrate superior mechanical ability if they want to nullify your strengths.
High skill cap assassins like hanzo, genji, tracer, illidan, medivh require outplaying your opponent to score an advantage where a zagara, gazlowe, vikings, murky can simply apply pressure and watch the map to wait out any aggression.
Do you really want exp suckers taken out? Have you seen ARAM dominating the brawl schedule since hots went maintenance? Is that experience really what you want every normal game to be just on a slower larger scale?
Those exp suckers apply a kind of clock to the game. If you choose to brawl and not respond, you lose a fort, then your opponent gains passive exp and catas. So you deal with the strong early game laner now in resourceful way or you lose by attrition.
I think that addressed your point, I’m really not sure what you’re looking for since you’re rockin the medivh portrait - ironically the only hero that can soak indefinitely while being permenantly invulnerable…sooooo whatcha want?
PS, before the experience/tower changes where blizzard altered hots to cater to people specifically with the point that you’re making, a whole host of absurd non-meta drafts were possibly by utilizing range, poke, stalling and outlining a win condition at the start. For example, lets say its cursed hollow and you’re running up against a standard pick comp of diablo, genji, greymane, tyrande, and abathur. This is a very aggressive dive comp that lacks waveclear and requires picks. So what I would do, is grab azmodan, murky, chromie, ragnaros, and nazeebo - 4 of which are exp suckers. By stalling each tribute with anti-siege tools and carefully watching the map, you can do camps and squeak out an exp advantage. But some people find that playstyle convoluted, counterintuitive, slow, and boring.