Mana passives and ability costs

I feel like riots had a historical problem with designing champions that have mana passives. One of the biggest design philosophies when you design a moba is how you design your abilities, you either go the dota route where abilities are extraordinarily powerful and impactful at the expense of crippling downsides, basic abilities that stun for five seconds but need to be fired from a thousand units away or a taliyah ultimate on a basic ability that also stuns for two seconds anyone near it or you can design your abilities like heroes of the storm where abilities are used constantly for no cost on any target you feel like all game long but because of this none of those abilities are allowed to be impactful, id give some specific examples but theyre all so pathetic none really spring to mind and is primarily the reason i dont play HOTS.

The most basic downside you can add to an ability to impact its usage is mana cost, with dota's impactful abilities its not uncommon for a hero to only be able to cast TWO spells for their entire lane phase without having to spend gold on mana potions. This leads us to league of legends which sits in a comfortable middle between dota and hots where spells arent as insane as dota but are also much more spammable so you get to use them often but when you do you feel rewarded. However when riot designs a champion with a passive that gives them mana then obviously the strength of their passive allows them to exert additional influence on the lane over other champions with more direct passives right? You would be wrong. Riot seems to think that because a champion has a mana passive that means its okay for that champion to have high mana costs, to the point where the passive doesnt do anything for the champion because its salvaging their manacosts rather than bolstering it. Cho'gath not so recently but recently enough had 30 mana cut from his primary ability(his Q) and i cannot explain how much of a world of difference its done to make playing him more engaging even though the mana gains he receives is fairly small.

The reason i made this thread is, shockingly enough, zoe. Zoe is riots latest champion with long range poke, her poke at level 1 costs her only 50 mana. Thats not to uncommon you might think, its her main damage ability after all and she needs to use it often. But compare this to xerath whos man damage and poke ability costs him 80 mana, thats over a 50% increase. But what about the scaling? Zoe's increases by a pitiful 5 mana per level capping out at 70 whereas xerath's goes up by double that ending up at 120. Zoe's max level ability costs less than level 1 of xerath's .Hell lissandra, who casts her primary damage spell every 3 seconds STILL costs 5 more mana than zoe(and a whopping 25 at level 1) her reposition ability costs 50 more mana than zoes(this is double the cost) as well