Yes. That wouldn't be my only adjustment, however I do believe it would help better incentivize PvP. Most of the PvP mounts have been simple reskins, which doesn't help incentivize non-PvP oriented players. The devs refusing to budge on grand company restrictions until recently only further deluded interest. People were queuing for gear and Fenrir pup though, but instead of expanding on this, the devs kept adding new stuff to each new map, effectively destroying all previous modes. If they consistently updated stuff you could purchase with Wolf Marks and better improved PvP as a whole, people would be far more likely to at least try. And that's how you build a community.
And what you just said is incentive. People continuously run dungeons because the rewards are good. Granted, that isn't the only reason. They're simply more entertaining for the majority of players. Frankly, I'd argue the faceroll aspect is actually hurting dungeons, but that's another discussion. What does PvP offer? Nothing. The rewards are self defeating (see above) and little is done to incentivizing non-PvP centric players. That's part of the issue. Games like Overwatch can dedciate the bulk of their updates to PvP partly because the foundation is solid. The Feast was a major update and yet it trickled off and now they're back to throwing mounts and minions in a desperate hope to lull people back. It just isn't going to work. Coincidentally, you aren't given any exclusives for being a good Overwatch or Battlefield 1 player. I could pick up either game now and earn everything veteran players have except promotional crap.
Now if we're going to discuss wholesale changes, I'd do something along the following:
- Scrap and/or merge all PvP exclusive abilities. Button bloat is enough of an issue in PvE Stormblood is purposely doing away with abilities just to avoid it. Adding six new abilities only makes the barrier for entry that much higher, thus pushing people away.
- Create and update stuff obtainable through Wolf Marks. Imagine if say, the cosplay gear in Veteran Rewards had been purchaseable through PvP? How about Umbrites? Or old gear from 50 dungeons so you didn't have to hope RNG liked you? All provide some means of incentivizing players.
- Implement rank depreciation.
Yes, it will need dedicated attention to keep people playing, however you first have to get them in there. A timed exclusive won't do that.