[Firestormalpha]

Never really gave much thought to the hirelings myself. This is what I discovered on the battle.net website:

Attributes and Experience Hirelings in Diablo II: Lord of Destruction come with their own set of attributes: Strength, Dexterity, Health, Damage, Defense, and Experience. As Hirelings kill monsters, they gain experience points. When they gain enough experience points to reach a new level, their attributes automatically improve. You can also improve their attributes by equipping them with better equipment (see below). Keep in mind that Hirelings aren't just paid mercenaries--they are co-adventurers. They fully share experience for their kills with you, and they receive a smaller share of experience for monsters that you kill. Mercenaries do not get experience from party member kills, but they do from your summoned monsters/characters. Hirelings will not gain experience once they have reached your level. They will begin to gain experience again once you level up. Hirelings might not level up very well if they are in areas where monsters are much higher in level. You might have to try different areas to find good places to level up your Hirelings. Try to keep your Hirelings near your character level. Always quickly resurrect them so that they don't fall further behind. Hireling Levels Hirelings cannot level past your current Character Level. The only way you can get a Hireling that is a higher level than your character is by buying one at that higher level. Hirelings at a higher level will not level up or gain experience until you catch up to their level. Often they will not level up until you level up. Once you have leveled up, they will quickly do the same, often in a few hits. Hirelings have a maximum level of 98.