I am also hesitant to have 2 hirelings, 2 underlings, and 2 followers at the Safehold I level. It seems like a lot. That said, I don’t know how many people will get to that level, given the likely cost. But it might not be a bad idea to either (1) reduce the number of slots in the progression, and/or (2) offer different effects than just “more, bigger numbers.” (Ideas: Items that give free movement, let you see invisible, negate the 50% miss chance for incorporeal, provide a re-slide, provide more types of damage reduction, negate fear/charm/curse, etc.; these could even progress from 1/game to always on).
However, I would not assume that all players who use a hireling, underling, or follower would opt to maximize damage. My first thought upon seeing the various options was that a +2 saves hireling would let me drop my IS Tanzanite Cube, and a +1 foot item follower would let me add Boots of the Marauder to my Boots of the Four Winds when I need free movement but don’t have room for Bead of the Lucky Traveler. But some people probably would go with all damage all the time. It’s a lot to balance.