Short version:
No Dragon Age Inquisition type big and empty maps filled with creeps that don't even make sense being there in the first place.
Lots of dangerous random encounters -> hell, let me fight an army if I think I am tough enough!
Longer version:
Many games make the mistake of making these a little bit annoying rather than fun, feeling more like an ammo-waste-encounter to fight weak mobs that force you to put away your BFG and use a boot to the head.
I would really love to see them more challenging and also more rewarding (get my damn ammo back) so that one can get the option of farming a bit of XP to level your char. This was done really well in Fallout 2 for me where you know that venturing around certain areas had certain types of enemies roaming (Remnants of the Master's army) so you won't venture out too far whilst being weak.
I know the focus on gaining XP is mainly on missions but if this is done right, the random encounters can be a lot of fun..An example would be that if you are in an area with weaker enemies (raiders or whatever), make them plentiful (which can scale a tad with your level but mostly in the area you are in). The 1 thing I had against WL2 was that if you didn't milk all of the XP out of a mission/area in the main story line, it wasn't easy to make up the difference with decent roaming/farming. This forced the obsessiveness in me to go lock-pick/hack/whatever little thing in a map just so I don't lose out on XP.
You can always sneak in a side-quest with a mean boss that would make you wish you did in fact, level your chars a little bit
