The Heckler just costs 1 less than Booty Bay, while the new Rager simply has one extra health.
A lot of people are complaining about this, yelling about power creep and laziness and greed. Blizzard has been pretty careful about this though, as I am sure they don't want to really tick players off. Both of the cards that were completely obsoleted were terrible cards that nobody played and both were free cards that came with the game. You couldn't have wasted your money or gold or dust or anything to buy Magma Rager or Booty Bay Bodyguard, so that limits the outrage to some extent.
So these new cards aren't ruining anyone's investment, and they aren't changing the metagame in any way that matters because the replaced cards weren't *in* the metagame in any meaningful way. Heck, the new cards aren't even especially good - Heckler might see some play, but I am not especially impressed, and Ice Rager is still terrible. (Which shows how bad Magma Rager was!)
Given this, the charges of power creep are completely unfounded. There are plenty of new, powerful cards in the new set but these ones aren't the ones pushing the limits.
But should Blizzard really be printing strict upgrades like this? There is one other absolutely strict upgrade that I can think of, which is War Golem and Dr. Boom. Dr. Boom is legendary so you can only have one of him in a deck but I don't count that as a relevant disadvantage. War Golem is a absolute trash card and Dr. Boom is one of the best cards ever printed so it is rare to see them talked about in the same sentence, but technically it is an example of existing strict upgrades.
I don't think there is any compelling reason to complain about power creep here. Blizzard is realizing that minions with low health aren't good, especially ones that are designed to be defenders like the ones pictured above, and that means they need to adjust their formulas. This isn't a matter of power creep, it is a matter of using the whole design space and not feeling limited by old cards that turned out to be complete rubbish.
From an aesthetic standpoint though, I wish they would do something to change the old cards.
Blizzard could simply add one attack power to all three of the strictly worse cards and it wouldn't change the amount they got played but it would mean that they don't look quite so sad. None of the three would end up in constructed decks, all three would be better picks in draft, and nobody would be able to complain about new cards being strictly better than old ones.
I think Blizzard has taken the tack that they aren't going to buff old cards though. They want things to stay the way they are and will just print their way to a better set of cards for the format. I can respect that decision - interfering with cards already printed does irritate people, so it should be done as sparingly as possible.