But it’s also likely to be a small amount so not noticeable. It’s not like ding OMGZor! Teh Mobzs now all have a treeeeellion health and dps.
Besides, you’re complaining that it would make the game trivially harder for a short period of time (before you equip a better item) while everybody & their dog is complaining that the game is so easy for the majority of the campaign.
A: 
B: You’re wrong because you’ve never experienced a good one. It’s like telling a child that a thing can be nice but they refuse to believe you because they’ve had one bad example.
C: Your opinion is both subjective & not the only one.
That depends on the skill & the skill point you put into it, but early on the next tier of weapons are often more of a power bump than 1 more skill point. Aaaaaaaaaand, if the power you get from skill points is that trivial (when they really aren’t, but again it depends on the skill, they can be for older skills) then why do people complain that too much player power comes from skills & not enough from gear? Perhaps you should just get better gear.
I also find it amusing that you think that 1 additional level for mobs would be such an insurmountable jump in power but that 1 additional skill point would be so trivial. This is clearly why people complain about relevelling skills, that the amount of power they feel they loose is so mind-numbingly trivial that they can’t bear to loose it.