If you're able to go 30 instead of 28, you might consider the WTB Exposure 30c. They are tubeless ready and gum walls (genuinely not sure why you would care about that). As near as I can tell (quick Google), they don't come in 28 width.
The WTB 30 gumwalls came on my Cannondale Synapse SE 105 alloy. I am still getting used to the bike (less than 500 miles on it), so all I can really say so far about the tires is that I don't hate them. Today I rode a half century, and I pushed the tires in curves harder than my previous rides. They feel good so far.
I checked bicyclerollingresistance.com and unfortunately I don't see them tested.