ok. Aside from my personal point of view that you can play competive with every merc (your skill is the deciding factor of your sucess not the merc).
Lets see. The current mercs that are usually desired for comps are Fragger, Vassili, Bushwacker, Skyhammer, Sawbonez. You can only bring 3 on your own. You allready got Skyhammer covered from day 1.
You get a nice fat credit boost with the first couple of lvl. that will allow you to buy one of the 30k either Vassili or Sawbonez. In 2 weeks you can grind the other (if you are good or grind a bit harder you can even afford one of the 50k). Boom playing skill aside you are ready to play the game the same way the best teams can. add the free rotation ontop and you are more than ready.
We are not moving any goalposts we are taking the literal meaning of Pay to win. You have to invest real money to increase your chance of winning / progressing in the game. which in DB you don’t have to.
Your examples F2P:
Guild Wars. is a fullprize game. You have to pay before you get anything conversely I would expect to get everything for my money (if they turned F2P recently my bad but point still stands the game was paid in full by those that bought it. Any F2P money is just a easy cashgrab now).
Path of Exile. Yes a nice model I agree. But I’d like to point out that as a diablo like grinding for better gear (random drops or trough shops) to stay competive with other players and against the enviorment is the whole gameplay.
Warframe and convenient account options.
I played WF quite alot and I think their system is fair (the colorpalette Idea was genius and made me cash over pretty fast). But is it better then DB certainly not.
You have to grind constantly in the game. Everything is locked down behind grindwalls and randomdrops.
Want a new frame (consider that the analogues to a merc) you have to get blueprints (credit grind). You have to hunt down parts (credit and random drop grind). Once you have everything you need to wait several days, till it is built up. Then you have to level up that frame, to unlock all his abilities. To improve him further you have to use augmentcards (random drop) and can increase the ammount / quality through special items (grind, random drop, waiting for events / alerts).
The same applies for pretty much anything in that game (i.e. weapons…)
All or parts of that can be bypassed by throwing money at them.
Furthermore Warframe uses a limited loadout system. You can only increase the amount of Weapons and Frames that are avaible to you by spending real money. Want to try out a different frame/weapon but have no slot tough luck sell one of the other. Realizing that the new frame/weapon is not to your likeing and you want the old back? Well you gotta build a new one from ground up.
In DB you unlock mercs permanently and will always have access to it. In games that limit your inventory you can never get everything unless you pony over money no matter how long or good you play the game.