Linked Spawns
I understand that the idea behind this is apparently to encourage players to explore, but there really needs to be a logical progression to it.
To illustrate what I mean. There's a newbie dragon quest that asks you to go kill tiny grass beetles (lvl 4+). The quest only tells you to about one place where the beetles spawn (take a right at the first fork, they're down by the sand beetles), but give absolutely no hint that there's another, much less where you might find this other spawn.
Once a player gets there they may be lucky to find a few beetles to kill, or, if they're unlucky, have come after someone else has wiped the spawn.
Now most players are going to see that these higher lvl beetles are near the lower lvl ones, so they're going to assume that more must be near.
If they head down the road they were one they reach the sandbeetles.
Take the fork right where the lvl 4+ grass beetles are, they run into wolves/undead.
Heading back to where the lvl 1-3 grass beetles are; if they go back towards NT they find only grulets, and heading towards the fallen log they'll find brown spiders.
Most players are going to stop here because there's absolutely no logical reason for them to search beyond this point. The grass beetle spawn stops at this point; there's no mixing that would indicate that maybe a player should just head down the road a little bit further (actually its nearly on the opposite side of the island from the first spawn).
As a veteran player of just over 4 years I had absolutely no idea there was a spawn down that way until a week ago.
Another, more extreme, example would be the snow (or is it ice?) beetles that are found near Mahagra/Snowfall and also Trandalar. Now it is possible the quest has changed since I last played thru that level range, but back then, I spent several frustrating hours looking for more beetles to kill for the quest before complaining in dragon chat only to find that the beetles are linked to a spawn on Trandalar. What possible reason would I have to go search another continent, when the quest text mention nothing about it?
tl;dr version:
A player needs to have a reason to believe they may find another spawn of whatever in order to go searching for it (i.e explore). A player's not going to think that maybe the other spawn region for this creature is across the island, or on another continent. When they kill off the region they're in; they're going to look in the immediate vicinity. If they run into nothing or a completely different type of monster, they're not, typically, going to think that if they keep going they'll find more of what they're hunting for. Same if the quest only mentions that one area.
