Favored foe does not require a spell slot, nor does it require a known spell. I think it is hands down better than favored enemy.
HM is a spell, so it should be better, but it is one spell of many a 2nd level can choose and one spell of two a second level Ranger can cast.
Using your own math you can have +1d6 for max 2 hours a day. You have another 22 hours without it and any fights in that time, or after you fail concentration will not have 1d6.
Did you look at the XP/leveling rate at level 2? It would take very trivial fights, or fake fights that scare a cast of HM, in order to not gain a level after 2 hours of fights.
At level 3 you are up to 3 hours of fights.
And no, "it uses a spell slot so it should be better" is silly. By that argument, anyone who cannot cast spells should suck. FF requires a class resource, a bonus action and concentration.
At level 1, the Ranger gains a weakened "martial" tookkit (d10 HD, martial weapons, medium armor), an exploration feature, and favored foe.
The Fighter gains a full "martial" tookkit (add heavy armor), a fighting style, and second wind (6.5 self HP/short rest)
The Paladin gains the full "martial" toolkit (add heavy armor), divine sense (exploration feature), and lay on hands (5 HP/long rest).
The Rogue gains a budget "martial" toolkit (light armor, d8 HD, restricted weapons but not meaningfully given sneak attack), sneak attack (1d6), expertise (exploration/social feature), and a ribbon.
The Artificer gains spells (1 level earlier), d8 HD, budget "martial" (medium armor, simple weapons), and a ribbon.
At level 1, the Ranger is meh overall.
The real problem is, as noted, that on top of the feature being meh, it
doesn't work well with the Ranger after level 1.
If you removed concentration from it at level 5 it would make it feel much better. That avoids dipping, and helps the Ranger scale a bit. Sadly, the problem is that the feature it replaces is so crappy that it then becomes a mandatory change to produce an effective Ranger.