It shouldn't really matter if you're flying in IMC or VMC with the hood up, you should be looking at the instruments
No you shouldn't you should be seeing and avoiding. Just because you are IFR doesn't mean you should ignore the basics.
Just look at the airprox reports of the amount of aircraft who are IFR reporting when they are flying procedures in class G airspace with no protection in VMC. Then **** themselves when an aircraft gets close. Heads down make sure the needles are right.......... Hells bells where did that come from.
I have got to within 30ft of a microlight before in CAVOK flying vectors under a RAS or a deconfliction service as now is. It painted on the Radar twice in 30 mins for 2 seconds each time according to the investigation.
If it is VMC you are duty bound to lookout.