exactly.. people are freaking out.. but the f2p mechanism is identical to Hearthstone.. and frequent hearthstone players rarely complain about lack of dust (basically what credits are in this game). The same reason you see so many gold cards on streams

They literally have nothing else to do with all of the dust.
That's what this game is going to be like.. if anything I am guessing blizz is going to put something in at some point to siphon all of the credits off.
below is after already spending about 2500 credits, after opening 120 boxes and currently level 13. Give me a sec and I'll count how many leg skins I have
Yep, I've opened ~135 boxes, which is about as many as I had in closed beta before microtransactions existed, and I have roughly the same amount of shit now as I did then, which is to say: Everything I REALLY want and plenty more.
I have 3925 gold, 459 unlocks, 25 epics, 11 legendaries. I bought 2 of the legendaries, so 9 out of 135 boxes. plus like 6 thousand gold. I also bought a bunch of voice lines just to get the 40 unlock achivement, so those were kind of a waste but fuck it gold is o trivial to get who cares?
And my point in this isn't that I spent money, although we can come back to that, it's that this is a pretty reasonable amount of playtime for someone to get in a month to be totally honest, and have all of that EASILY, and not just 'randomly' those numbers, but easily buy what they want in those numbers. I could have 4 more legendary skins immediately if I wanted to, I just don't need any more.
Similarly, in terms of cost-value, I've spent 80 bucks on microtransactions and gotten effectively 10 legendary skins from them, plus all the other drops. that is unfucking beatable from a value proposition for this type of transaction. A skin would cost 10 bucks on its own if this were most games. Instead I've gotten those 10 skins, counting what I could buy with gold obviously, and ALSO 90 other fucknig drops, minus whatever dupes contributed to the gold. Let's be generously low and say I got 30 other drops that were real (in reality it has to be closer to 75), that's fucking fantastic.
12 weapons = pick between 90% of hats. Play an hour a day for a few days a week, and you'll have a hat in a week and a half. Considerably slower than in OW, admittedly, but not quite the "ZOMG lucky to get three hats a year!" you're playing it up as.
But again, let's remember OW's up-front cost. $40 in TF2 gets you hundreds of hats, which you get to choose. $40 in Overwatch gets you the basic game.
In terms of comparable drops for high end?
literally zero.
This would be like if OW easily gave you blue skins (like it does now) analagous to regular hats, and you basically had no chance of acquiring a legendary skin without dropping 100+ bucks on the marketplace.
Let's make this even simpler:
TF2's drop system is the equivilent of if a Legendary skin in overwatch COULD NOT be gotten in the game for free, period, but you could open a crate for 2.50 and have a 1% chance of getting one.
Average price of a legendary skin being 250 dollars sounds dope as fuck sign me up.