I don't agree with mages and the heavy mana gateing.
Obiously some kits need gateing either just for lane or even later on, but in general, heavy gateing through mana leads to a very passive and boring playstyle as you only comit your preccious mana if you really are sure to get something from it. The insane mana gateing is one off the things i dislike most in dota.
You also shouldn't forget that in dota, even mages have well scaleing AAs, some of them like lina even have pretty huge dps, so they can afford to hold back their spells.
Imo mages should rather work like in S2, when you actually had to decide between cdr for dps and raw burst damage. They should be more gated by CDs and opportunity
Assasins imo should not be designed about 100-0 combos, wether it's delayed or not, it always leads to a binary scenario where either the victim or the assasin gets rather frustraited(Zed always had the delay, and by times was the most banned champ in the game even while not op). Imo they should focus more on hit n run, beeing able to unload decent damage rather fast, and then disengage for a second round soon after, while skirmishers should have an ok opening burst, but good dps and stickiness aswell as the means to avoid some damage so they can use their dps.
Fully agree on adc, they need more rampup mechaincs and shouldn't have burst mechanics like shiv on their dps items. It's ok if they can built ad/cdr/pen and become ad-casters that have burst/poke, but they need to sacrifice dps for that.
I also really dislike current huricane, crit+aoe should not go together. Old hurricane was a lot better design, you could go for on-hit builts with it for aoe damage but loose out in the crit scaleing vs singletaregts, so there was more of a tradeof. They also should have to sacrifice a bit more damage for survivabillity than they currently do, and lifesteal items should NEVER have anti burst/anti cc on them, they should counter their own counter.
But mostly, crit needs to go or geting reworled into something else, but the current RNG has no place in a competetive game. Pure luck should never decide wether you win a trade/fight or not.
Supports imo should be less designed as slaves to the adc and just the adc but rather more as supports for the entier team, with maybe some beeing more focused on supporting adc, some on helping melee fighters and some on boosting mages. I also do think that (some)supports should be allowed to be somewaht selfsufficient, especial earlyer in the game. It really helps strategic diversity if there are supportive champs that can perform in a sololane while getting his best perormance once he joins up with others. And yes, i'm all for supports working more through others rather than for them with stuff like namies W or Ivern E.
Tanks should have less damage+cc, right now they bring to much of both. Befor the tankreworks slapped aditional cc on every tank, it was fine for them to do the damage they did, but now it's just to much output overall. They also could use a clearer focuse on either engage/dive or peeling. Prettymuch all tanks right now can do both so there is little varity. I also think that hard cc shouldn't be as plenty and spamable as it is. It needs to be either gated by high CDs and/or by Opportunity/Conditions. Maokai spaming a strong aoe knockbak every 3 sec or Zac haveing 3 displaces in his kit with not to high cd on two of them is just to much. It's ok for a tank to be disruptive, but there always is a line that shouldn't get crossed, and the old tanks imo were well within line, they had good cc to be disruptive, but weren't overbearing with it.