Disease resistance seems to be very good. However, this cultivar appears to lack cold hardiness in a Zone 3 climate, which one would expect from its genetics. It's not as cold hardy, for example, as 'Campfire'.
I live in Ottawa zone 5b I planted Never Alone in September 2016. In November , it was black spotted badly. I checked today (27th March) my rose. There are many canes dieback despite being covered with several feet of snow during the winter. The good thing is i can see new thin green canes emerging from the ground. it seems that this rose is not cane hardy here in zone 5
Now that Ive had it for a bit, I can say this. The spring/fall disease resistance is poor. Its quite susceptible to moderate temps w/ damp weather. I am not sure if its downy, cercospora, and/or anthracnose. The 3 of them differ by cultivar, and ifs there's a lot its like good luck ID'ing that without staring and leaflets for way too long (I got other things to do lol). The summer health is good. The plant shape is good. The rebloom is quite good. The color is good but the flowers do not like the rain one bit.
Its parent, Yellow Submarine, is 10' away and bothered by none of these things.
It's real highlight is how small of a rose it is. Very short and blooms a lot. The foliage is truly the issue, and seedlings have had the same issues. Honestly, it would be in the compost if the mood ever struck me.