I'll tell you.
Warlock: Master of the Arcane (published by Paradox) can't be played without the Steam client running in the background. Period.
Warlock is no in-house production. Paradox only published it and, like Naval War, the game is a full SteamWorks title. Paradox' own productions, like Hearts of Iron 3 or Crusader Kings 2, are not SteamWorks titles.
What makes you so sure EU4 will be any different?
i never said i was sure, in fact i stated plainly that it's a guess based on past practice on Paradox' part. it's entirely possible that Paradox will go full SteamWorks even with their own productions. already they've started selling third-party games in the form of Steam keys. i welcome this as it means i don't have to install half a dozen different copy protection drivers.
Then it is as good as GOG for me and absolutely DRM free. However having Steam only for these games seems a bit laborious for me. If Paradox really doesn't need Steam at all they can make the minimal effort to offer their game also in other places. That's a question of good service then.
you're simplifying things. Steam is attractive for DLC distribution as well. Paradox do a lot of DLC. Crusader Kings 2 has its own system regarding the purchase and use of DLC. apparently, the effort wasn't profitable for Paradox, compared to the Steam edition, so it's not unlikely they'll scrap GamersGate editions for good and sell only SteamWorks keys. they've started doing that with third-party games already.