What procedure do you follow in setting DCs?
If I'm setting DC's then I've assessed the difficulty of the task/obstacle to be risk-worthy and thus a roll is required. Character level plays no part in the decision-making process for me.
I usually decide what would the DC 10 benchmark equate to for that particular task/obstacle and take stock of factors which notably increase the difficulty of the task/obstacle in the fiction. If the PC's have any realisable benefits I would allow for Advantage on the roll.
As an example for
Dexterity(Acrobatics) or
Strength(Athletics) checks, player can select.
[05] Crossing a wooden bridge (NO ROLL)
[08] Crossing a wooden rickety bridge (NO ROLL)
[10] Crossing a slippery wooden rickety bridge
[12] Crossing a slippery, unstable, wooden rickety bridge
[15] Crossing a slippery, unstable, wooden rickety bridge in the middle of violent winds (possible fantastical location)
[18] Crossing a slippery, unstable, wooden rickety bridge, in the middle of violent winds and a blinding fog (possible fantastical location)
[20] Crossing, in haste, a slippery, unstable, wooden rickety bridge in the middle of violent winds and a blinding fog (likely fantastical location)
Using safety gear would likely provide Advantage on the roll, except in [20] since the obstacle was performed with haste, which means there was likely no time for preparation.
In this type of scenario failures would usually result in a fail forward or success with complication.
If a second roll is called for, and that was a further fail, then I'd max the complication or see the person fall off the bridge.
As an example for
Intelligence (Knowledge) checks
[05] Recognise the creature
[10] As above, aware of natural attacks, defences and abilities, knowledge of basic lore
[15] As above, aware of supernatural attacks, defences and abilities, knowledge of advanced lore
[20] As above, aware of possible weaknesses, knowledge of esoteric lore
[25] As above, knowledge about this specific creature's past (named creature)