I'm not convinced looking at the amount of ice at the top entrance is indicative of much, apart from confirmation the colony is still alive. The amount of frost outside the entrance depends on the outside temperature, humidity, wind, and on characteristics of the cluster. The frost outside the entrance doesn't grow indefinitely, it seems to reach and then maintain a certain size until conditions change. 

Yes, I would worry about ice build-up inside a colony with both no top insulation and no upper entrance. I did that set-up in 2015-2016 with one colony and I had copious amounts of water flooding the bottom board in the spring. The bottom board on that hive was a slightly off-set honey pallet and I remember the whole pallet flooding with water. I was having to tip the hive repeatedly to drain the water. In other words, I think a top entrance is also important in an uninsulated colony. 

Tracey 
Alberta, Canada

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