Again, I've already listed the reasons why you'll get instanced based over 'open world', but I'll go over the one you've overlooked again.
Having instance based insures activity for anything objective related. Without it, you're talking about roaming an empty zone when objectives cannot be completed if you're playing during in active times. For Frontlines - having enough people to actually participate in the core Objective mechanic is a prerequisite for the instance to exist in the first place - guaranteeing that objective based play and team play are the priorities. Short of that, yes, is Anarchy PvP, which really is the only innate value of open world.
So don't pretend you are compromising. Frontlines is the compromise already. Large zones with many modes and multiple objectives enticing groups to split and diverge as needed. Asking for continual compromises until you actually get exactly what you want isn't compromise.
And to correct another argument based off of fallacy - for those who don't remember - Slaughter was not objective-less Deathmatch. It was point-based deathmatch and the largest portions of points were off of NPC targets at specific locations that re-spawned regularly- which wasn't all that different from Shatter, except if you think of the ICE as capable of fighting back. I still prefer it to Shatter, honestly.
So, here are your list of reasons why not:
- Instancing Guarantees adequate participation in order for the event to occur - Open World does not. (This also prevents the need for a World Timer on events and allows people to do an event when there's enough people available - and not be limited to an arbitrary schedule.)
- Instancing Resets the map regularly so lingering map objectives (think PvP forts) do not become monopolized for long periods of time. - Open World frequently have favorites/dominating groups per player pool.
- Guaranteed participation assures that groups are (for the most part) balanced as far as warm bodies go (not class balance, this is more or less on the player base) This is better enforced in 4v4 in which the parties are actually forced to be balanced - we'll see how balanced something like Rival Wings becomes. Open World does not regulate this by default almost guaranteeing unbalanced participation. The only way to resolve that would to make it single-player queue only to evenly distribute forces,which would not go over well to any PvP community.
- With Open World the likelyhood of one on one combat would necessitate better balancing of classes for 1v1 combat - and SE can't even balance Teamplay here, let's be honest. But at least with focused objective play they have less factors to work against.
There is so much that can and does go wrong with Open World that a development team focused on making PvP accessible, fun and team-centric (Remember, they're looking to MOBAs and other E-Sports for inspiration, which is pointedly not Open World) is not going to look at Open World and think "Yeah, we can handle this workload." This is not including how notorious SE is right now with the breath and depth (or lack thereof) of PvP right now. This isn't as easy as programming an instance. You're asking a major undertaking that is severely divergent in both development and theme.
It doesn't bother me that you want it ,but you generally don't seem to get that the moment you ask for Open World, you're not asking for a compromise, you're asking something extra. The game would still be healthy if PvP did not exist. PvP would still be going on if it was just The Feast or the Fold, and they added decent rewards to that. But they added something large scale with decently large maps with varying objective styles - Frontlines. You're asking them to cross a line and created something constantly open - there is no compromise to that; just debating the rule-set within the thing you would be getting.
Given all of this, this is what I speculate they will do:
They will likely continue to add different types of Frontline content to continue to satisfy the objective desires contained in Open World play, while addressing Open World's faults - one of the key components of that is keeping it instanced. I simply don't see enough of a reason for them to cross the line to Open World PvP, when they have a multitude of readily available alternatives.
But don't feel alone in this frustration and disappointment - there's very little to be said of Open World PvE content either, which is another reason why I feel crossing that line for PvP isn't something they're going to support.
As far as my personal desire - I don't want it because I know they won't do it right. PvP needs to be built well from the ground up with a large development team behind it. While I do enjoy a bit of the PVP we have going now, I don't have the confidence that SE has the capacity, nor the motivation, to make that level of investment and make it right. I'd rather they not do it than to get something potentially more catastrophic than Diadem.
So let me turn the phrase. Look at our track record for PvP and other content in this game right now. Let's set aside the speculation of 'should' or 'will they'. Tell me honestly, in your assessment, can SE, with everything we seen, truly make a satisfactory Open World PvP? I'm sorry to say, I don't think so - and I'd rather them make a separate project (game) from the ground up to support that desire.
Until then, I'll sate myself with the upcoming Dissidia game and Frontlines.