My very first impression of the land Istaria was how very small it is...The Island of Vvardenfell, from Morrowind, seems much larger, and is only a small portion of the overall land...it's like Lesser Aradoth compared to the mainland...
To create what would be, at least for me, a much more vibrant and intersting world would be to expand it greatly(Lesser Aradoth for an example)...make it take 2 hours torun from Kion to Sslanis, and make the monster spawns be huge and somewhat densely populated, and for heavens sake, make spawns overlap, please...Of course, patches of spiders and roaming herds of Gruok would be needed, but there should be threats all over the jungle. I think it is silly that you can sit just outside of a spawn area and pull mobs to you...I want to go out and hunt them down, not memorize where they are, pull one at a time till I no longer need those mobs and move on...
Also, I think it would be real neat to come across villages and small towns, heck, mabye even roaming hermits...It would be awesome to be walking along a jungle path, looking for any sigh of a monster, when there is suddenly a clearing to your right with a few huts and several Sslik standing/sitting/walking around, who can give you quests or just talk to you...A bit farther north, a roving band of Saris hunters walks around to random waypoints, giving you advice on what is in the area and where you should hunt for your skill level...
And for heavens sake, make the cities HUGE!!! Sslanis was so dissapointing the first time I saw it, I expected a grand city easily bigger than Tazoon is now, filled with Sslik moving around, merchants, trainers, children running around, empty warehouses, nooks, NPC's that will give quests or talk to you in the way a Sslik would...wary of outsiders, warm and friendly to other Sslik...So many games are plagued by tiny 'cities' that wouldn't be classified as towns...Tazoon should be as big as Lesser Aradoth is now, and divided into 'zones' (Bad word, I know) that would be accessed via gates...
And how about Imperial troops? Why arent groups of them guarding cities, hiring adventurers to travel with them to attack WA forces, recruiting players, out patrolling and scouting out the area and giving advice on what roaming monsters are near at this time...
And finally, mounts...Everything from horses to ridable gruoks for gnomes to tamed Ruxus for a slow but hard hitting charger...Make pack mules to act as, well, mules, a cargo disk that moves at the same pace as you, but can be killed by mobs, making you either buy a new one or find a to protect it...And with a larger landscape, having mounts would be the only way to travel, making travel times about the same, but making some attacks impossible and the rest hard after your initial charge has hit and you have to fight from horseback...of course, that horse might be killed, and now you have to walk or go get another one...
Just a few suggestion that I think would make the game a lot richer and attact more people...