King Rad
Warlord
Getting Lvl 3 is very very hard with recon units.
Interestingly enough, I haven't found this to be the case. My biggest problem has been losing them when I wasn't paying attention and they get killed in a battle [usually with barbarians] that I didn't really plan for. I often send two scouts out together, which with the flanking bonus can help both stay alive while exploring. With the barbarian hordes that can be generated now, especially the horsemen, it also often requires another unit in the early game to help keep them alive long enough to get that 3rd promotion. I also play with the unlimited experience mod which helps with the experience since I don't warmonger, so generally the only experience increases are from barbs and the various exploration points.