I want to start by saying that from a thousand feet I don't disagree with Izlain that Hereoes of the Storm (HotS) is a more mechanically simplistic MOBA than League or DotA2; but accessibility is Blizzard's wheelhouse and frankly I'd be shocked if they tried to be the next Heroes of Newerth. HotS is angling to be the MOBA for the average Joe/Jane, the person who doesn't want to spend hours researching item builds, buy a rune build for each champ/lane, a mastery page to match, and know each champion by magic defense per level.
I feel strange coming into this discussion with an apparent attitude of "In my day!!" but I think it provides some important context. Belghast disputes the team-play issues of last hitting and personally I agree; but at the same time I understand how it contributes to the strategy of the game as Izlain points out. Now for the "in my day!" part. My first exposure to MOBAs was in DotA...not DotA 2...DOTA, as in the Warcraft 3 mod. I spent long college nights when I should have been studying learning to play Venomancer and Broodmother (among my favorites at the time). There wasn't much of a meta back there, at least in public matches. You generally just matched the lane layout of your opponents and tried to win your lane. Concepts like ADC and Jungler weren't even really around yet. "Last-hitting" for gold was there because it was a limitation of the Warcraft 3 engine, the same with splitting into lanes to maximize xp gain. The designers couldn't figure an in-engine way to get the game to spread gold and xp out so it wasn't even discussed.
Fast forward to League and last-hitting was included because they felt like it added a dimension of skill. Note that League got rid of some of the other aspects of DotA that they didn't like, such as creep blocking and "denying" (the practice of killing ones own towers/creeps to avoid giving gold/exp to the enemy). I'm glad they did, because it always felt weird to me that in an "RPG" (despite it's competitive focus, League's premise is still that of a sort of arena RPG) you were encouraged to kill off your own forces. Maybe for the "evil" side that made sense, but for the "Good" side? Plus, how is it the magic forces that hand out these so-called bounties can't tell when someone just stole the killing blow from another who did all the work?
But I digress, the very meta the Izlain illustrates emerged because of an engine limitation; the idea that certain characters should split into lanes and the jungle was to maximize gold/exp. The idea of a Support emerged from choosing characters that did not require a large amount of gold to be useful thus could share a lane with the ADC (also originally a hold over from when Warcraft's engine couldn't do "spell damage" as a stat) and improve its effectiveness.
Last hitting certainly has a skill component, it takes learning and practice to know about how big the creep's bar should be for you to get the last hit in and how to position yourself to take advantage of this. It just also happens to be a skill, like micromanagement in Starcraft, that some love and some hate for perfectly valid reasons on either side. The choice by one game to eliminate it to highlight others hardly puts it outside of the MOBA genre.
Izlain links the following quote:
To me someone not liking the actual gameplay of last-hitting is like someone not liking questing in an RPG; at some point it’s not so much the game as it is the player needing to find something that better fits them. Just like an RPG doesn’t need ‘fixing’ by removing quests, the MOBA genre doesn’t move forward by removing last-hitting, at least not without a suitable gameplay replacement.
My greatest respect towards Syncaine, but I disagree entirely. One of the constant complaints about RPGs is the "Got to !, do what they say, come back to ?, collect reward." structure that has stagnated. Blogs name themselves things like Kill Ten Rats and comic artists made (very poor taste) jokes about an MMO character leaving captive citizens in caves because the player released their requisite 6. We applaud games like Guild Wars 2 that try to innovate on the system with more organic and public events or Archeage simply for letting you kill more than 5 wolves and get rewarded for it. The industry hasn't removed quests, but it's attempted to evolve them beyond the rudamentary core. That's precisely what HotS and it's ilk are doing by asking about the necessity of last hitting.-Syncaine
To say that last hitting is a fundamental of the genre is to say that any difficult-to-improve mechanic is; Quake's bunny hopping, Smash Bros wall-hogging,or DotA's creep denying are all things that were thought to be fundamental but were so immersion breaking (yes immersion matters to some even in competition focused games) or otherwise problematic that the designers removed them. The same could be said of last hitting. A MOBA is simply a game in which two teams play as characters with varying abilities in an attempt to destroy an opposing team's primary structure. Everything else is a mechanics choice. In the past people would have said that WoW's Valor points were not fit for an RPG, or leveling solo, or Personal Loot...all these things have been questioned and innovated on because they didn't work in the context of the gameplay the designer wanted. Last hitting is the same.
What it comes down to is a matter of subjective opinion; last hitting exists because of an engine limitation, to some it's become a cornerstone, to others it's a break in the immersion. HotS chose to be distinct by eliminating it and putting the early-game focus on objective control and teamwork. Let HotS be HotS and League be League.