You apparently haven't played wow recently then :P
1. Wow instances are zergable, infact I've had people just DRAG the entire mob army with them from the start to a boss, literally everything. This is very true for low level instances and or "normal" difficulty instances. (With a good tank anyway, some take it slow and pull 1 group of mobs at a time)
2. Technically you do have to clear bosses in an area in some instances or certain mobs, or hit certain switches "aka pop items" to spawn/be able to fight a final boss. (for instance dire maul requires killing and deactivating "arcane barrier consoles" to be able to fight the final boss).
3. There are item chests in wow (with sometimes "epic" gear) aka loot chest. If you do "random dungeon" you get tokens which you can trade in to get "Exp bonus gear for lvling or high level epic pve/pvp gear (or old world gear/content or crafting materials or mounts or pets etc etc)
4. Limbus back when I did it about 5-6 years ago was slow, you could do it with 2 BLM but it took like 45min+ (for like 1/2 the instance), sort of like you can do a 5man wow instance with 2-3 but it will be slow. With current content of both FFXI and Wow however, I doubt it takes every long even with a few FFXI and especially wow (5man instances I've done can be anywhere from 8min to 20min) namely because of bad players, I'm sure ffxi has bad players also however :P
5. Wow instances are tuned for a level range not gear (till your doing heroic/hardmode instancing very late in the game). Before that you can basically go in a high level "normal" instance naked with a gun if you wanted to and still get a group within 5-8min (yes I have done that, was trying to fix a gear swap mod).
Overall unless SE really changed limbus over the years I haven't played it (although I hear people just jump in abyssa at Lv 30 and go to Lv 70 within a day now?) It doesn't seem too different excluding the scenery/mobs :P
I doubt that Yoshi P will want a wow clone anyway though, as I'm sure in one way or another he's seeing the NA response to "ZOMG NO WOW CLONE PLZ THXS" spam on the forums so they will probably makeup something different.
I'm really hoping though, they don't do more world NM's... even with the current low populations, the world NM (namely just this one) Dodore is over camped, especially during JP hours when you see over 10 mules at the aether jsut waiting for the weather change O_o
I just recently crafted my own dodore doublet after all this time, because JP competition is fierce on here for dodore ;/