Yes, I'll have the same. The shroud should minimise the need for heaters but on the worst nights (as you're saying I think) they'll still be necessary. My fans suck air down towards the mirrors too so on wet nights would this increase the risk of dew on the primary requiring the heaters?
Also wondering whether it's best to run with or without the shroud.
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I often wonder about dew heaters. We go to so much trouble to get the mirror cooled and per Paul Hease and Bird you actually want the mirror cooler than ambient rather than warmer. I have thought it would be worth an experiment to get one of those AC units with the hose output and angle one on a stand to blow cold air on my mirror as an experiment to see what effect it has. AC air is also dry and are great for demisting the car windscreen. So it may also stop dewing? But on those nights where it would prevent an image wrecking problem of dew it would be worthwhile. Certainly in Florida/Qld or high humidity areas it would be a must.
I have not imaged with the shroud off mainly because I was worried about the small amount of light we often have in the observatory from transformer LEDs and in my case my computer screen around a corner.
But yes I think you could get some better cooling and air flow by leaving it off. Would it be worth it? I think other factors would probably influence the image far more but every little bit adds to the final result.
Greg.