Well, there isn’t a lot of improvising you need to do in a lot of cases. A miss is a miss is a miss.
The spider tries to trip you, they fail. You don’t need to go into details or anything like that. Of course this is failing a Bane, not a boon.
Also, remember, there is Success with a Twist that you can/should easily be using for the PCs. So if a player rolls badly on a Heal, you can say:
- The heal happens, but the strain in combat to get it to happen causes you to be stunned for 1 round.
- You manage to heal, but the mental/physical strain causes you to lose 3 HP.
- Roll 1d4!! for healing, however the focus required causes you to lose your move action next turn (immobile for 1 round)
etc etc. That is, IF you want it to go ahead and succeed, a failure can simply be a failure. IF a lot are happening then you can start to do success with a twist.
Are you and the players remembering:
- Focus Actions to gain Advantage on a Major Action
- Using Legend Points for Advantage
- Assist Ally Major Action
Since Perception Checks are just a minor action in combat, failing that isn’t any big deal, just move on with “You don’t notice anything noteworthy” and keep the action moving.
Out of combat, unless it is really important, they shouldn’t be rolling too much. The reason for rolling in combat is the added stress and need to react quickly to the situations as they happen. Outside of combat you don’t have that added stress, you have the time to stop and think and take your time. In most cases I don’t require rolls outside of combat unless they are truly important, or things the PCs might not normally be able to do or know.
Healing outside of combat I just allow to auto-succeed, and generally don’t even roll the healing dice. Only time I make some of that stuff be rolls is if they are multi-targeting something, or for certain boons that might be really strong potentially.
But basically, if out of combat, Boons auto-succeed in my games with only a few exceptions that are very situational.