2 manas 2/1 rush get free two minions later on deathrattle and reborn.
4 manas 2/3 put x4 minions at once with only one card and x3 of tem have rush.
Cost 0 5/4 divine shield rush, will be ressurrect later with a cheap spell and will have reborn, divine shield and… rush.
I think the rush keyword is not the problem, waaaaaaaaaaaaaaaaay better than charge, but for free in undercosted minions is ruining the game, should cost at the absolutely minimum at least 1 mana, but costing 0 in many minions now.
Everything comes for free break the mana system of the game, what is already in scrambles right now.
All mentioned minions need to have increased their costs in 1 mana, at the bare minimum.
The only thing that I see able to be an issue with rush is when you can synergize with other cards, which you have not mentionned except for one card so I will ignore that part for my reply.
giving your opponent a 2/1.
So on it’s own it’s not a 3/3 rush it’s a 3/1
For it to remain a 3/3 it requires either an additional card or trading with an existing minion, so spending another of your ressources, so it never is a “1-mana 3/3 rush”
Basically Hench-Clan Hogsteed with an additional 1/1. That one was a very bad card so I’m not shocked by a newer better version
Can be compared to a 2 mana elven archer with reborn that deals 2 damage, basically you get twice the benefit of an elven archer for twice the cost. Doesn’t seem that bad
Mother Duck is a worse Night Elf Huntress
Giving a minion rush is the equivalent of giving it the battlecry to deal damage to a minion with ups and downs, I don’t really see why you would want another cost logic than that