You might say that your competing against your opponents through the process of CSing, but this adds an unnecessary third element between you and your opponents, not to mention that this element is extremely tedious and repetitive.
Okay, so why do the large and small plants fight back on the garden map? This adds a third element that is extremely tedious and repetitive. You're playing against the computer and yourself, not your opponents.
Why do the angel and demon dude duel on the eternal conflict map? This adds a third element that is extremely tedious and repetitive. You're playing against the computer and yourself, not your opponents.
Why do the shrines on the sky temple have guardians? This adds a third element that is extremely tedious and repetitive. You're playing against the computer and yourself, not your opponents.
You're saying the game should be you and your opponents ONLY, fighting each other. That is a fighting game. Anything else to you is a tertiary element that isn't necessary.
It's fine if you think CSing or last hitting is bad design. You're completely entitled to your opinion. You've yet to provide any proof that it's objectively bad design outside of you thinking it is. Many people would say it's good design, rewarding the players that have honed that skillset and can gain an advantage over their opponent in a different facet of the game.
No MOBA will be objectively better than any other MOBA and you saying so makes the HotS community look like garbage. Plus, all you have to do is look at the numbers. If HotS really did have the best formula and was objectively better, it should be close to the top, yeah? It has about 4.5 million accounts registered worldwide as of July. Surely if the game was so much better than the other competitors it would have more players? DotA 2 posted 11 million uniques in Feb. of this year and LoL has 67 million uniques in January of 2014.
I like HotS. I think it's fun. I think League is fun. I haven't played much of DotA to form an opinion. They are three different games in three niches in the same genre. They are all great games. None is objectively better than the other. Some are subjectively better, which is fine, but you saying any one is objectively better than any other makes you look like an idiot and the people that play your preferred game look like assholes.