I could care less about the rule set that an MMO follows. They are not the same and you should not aim for it. Pathfinder is a turn-based tabletop RPG. As a rules set for a TTOP RPG, it works quite well. However, a MMO is not a tabletop RPG. The people who think it should work like that do not get the design issues and probably never will.
I already know that the devs know this – but many of the fans here just don’t get it . Persuade your fans as to why – and with patience, the persuadable will be persuaded. However, some of these fans are NOT persuadable under any circumstances. That’s life. Keep selling them books and they will still be your customers, just not your online players. That’s okay. Let ‘em rant, because that isn’t Pathfinder.
I do see, however, a number of things that CAN work and DO feel like "Pathfinder,” to wit:
1 - Class Abilities: Pathfinder has improved upon and developed a number of class abilities that serve to distinguish the class from others. Those abilities should form a tangible aspect of a class design.
For example, we know what Paladins are. A Pathfinder: Online Paladin should have auras; smite evil, and have the ability to confer those benefits to others. Similarly, we know that a Witch has a familiar, can fly, and can cast hexes like misfortune and deep slumber. Alchemists in Pathfinder throw bombs and can use mutagens to increase their stats and body size. While something like a Vancian based arcane bond is not likely to matter in PF: O, Wizards should be able to throw a weapon and have it return to their hands. They should get some sort of metamagic and should be able to craft magic items. They should get a scorching ray and get multiple numbers of them as they advance (never mind what damage they actually do or how often it can be used) Barbarians are all about rage and DR. Gunslingers are all about guns, deeds, and grit, Ninjas can vanish, etc..
Keep the recognizable iconic abilities of classes and make them do similar sorts of things which are somewhat intuitive and recognizable to a player. The underlying math, lethality and so forth is irrelevant. Let the computer game designers of the MMO be computer game designers of an MMO. Nevertheless, some of the iconic powers of a class need to be represented and unique because that’s what fans expect and that’s what keeps up the verisimilitude of the Pathfinder brand.
2 - Look and Feel: Pathfinder has a distinctive art direction to its characters and many of its monsters. Some of that is going to work well in a computer game -- and some of it is not. Cut the stuff that will not work for polycount and animation reasons and do it without remorse.
But when you get right down to it, Pathfinder is Wayne Reynolds' art style. Make that come to life? You are golden in terms of art direction. Fail to deliver it and you dropped the ball and will alienate customers. Sorry – but in many respects it really IS that simple.
Above all, keep the cartoony look to your characters. There are strong benefits to this. On a technical design basis, it reduces polycount. As we move forward in the next five years, PC Gaming threatens to go off a cliff and the desktop will not be the primary platform for this game. Accordingly, anything that reduces graphical overhead and makes it more laptop friendly is good. Any CTO who tells you what the GPU capabilities are of the expected users of this game 4 years from now is making it up. He doesn’t know. That’s an ENORMOUS tech risk, so the engine and art direction has to be HIGHLY scaleable.
If you went for something like the CANVAS engine for your art style? You would not go wrong in terms of artistic impact (tech/economic feasibility is another matter). Apply the CANVAS engine's style and Wayne Reynolds art and color palettes and tell me you wouldn’t drool to play that game.
On a less technical basis, cartoony designs also serve to make the game look unique. The problem with realistic 3d models , shaders and middleware environmental options all designed to operate within the tech limits of the hardware platform of the day is that it all ends up looking the same, from game to game. Seeing as you are likely to have to use middleware for much of your environmental organic effects, anything that serves to distinguish the look of the game from that produced by others enhances the value. In this case, it also delivers on the expectations of fans – so double down on Wayne Reynolds' iconics and cartoony goblins.
Blizzard made the right call with WoW. Some people hated it and it turned them off -- but you cannot argue with that level of success. I can confirm that there was a significant debate within BioWare as to whether to go cartoony with SW:ToR. BioWare decided to go a little cartoony with their art direction in TOR too -- and it was the right call. Some people complained sure, but some people always complain.
3 - Golarion: At Paizo's current publication rate, it is likely that there will at that time of PF:O's release be more game material written about the world of Golarion than any other fantasy world in the history of RPGs. Even the FR (and that's saying something, damn it).
That is a VAST treasure trove of IP. It's the one thing Paizo brings to the table which it does BETTER THAN ANYBODY ELSE, in or outside of the computer development field. Do not sacrifice this on anybody's sandbox altar. Dance with the girl that brung ya.
That's what a Pathfinder: Online is to me. It's not rolling a 20, it's not Vancian Magic, longswords which do 1d8 or even magic missiles.
Gimme a Witch that hexes with a fox familiar, a chance to interact with the iconic characters which LOOK like Wayne Reynold's art come to life -- all set in a believable slice of Golarion.
That's a Pathfinder MMO to me.