I'm coming off a BLX Pro Open that I had weighted a little at 3 and 9. I think the 2 have roughly the same static weight but I think the Pro Open is still more HL despite the lead and that is what could be making the difference in terms of arm tiredness.
I think this is a significant issue for you here. I've always been a fan of heavier racquets with significant HL balance in the neighborhood of 10 pts HL. Sampling lighter racquets is always tough for me when that racquet only has a few pts. HL balance, even when that racquet is lighter than my regular 12+ oz. players.
I tried the new Blade 98 18x20 last weekend at the club where I work. Smaller 4 3/8" grip size than my usual 4 5/8" Volkls, much less HL balance than I prefer, and this demo was strung with a full bed of poly... I never use poly. The difference in balance with this Blade made me work hard for a little while to adjust to its behavior and swing with mildly different timing. I could imagine it would be rather rough going out to compete with this racquet without any time for adjustment.
Upside? I thought this racquet was terrific. I'm actually contacting the Wilson rep I met Saturday to help me buy a small package of Wilson gear including a pair of these Blades. I've been looking for a "work racquet" to use at least over there, but haven't liked anything in the Wilson stable until this one.
Enough plushness to feel rather good to me, even with a full poly bed, and a very civilized player. No issues with spin production for me, probably because of the overall lighter weight, and I was even rather comfortable hitting my one-handed backhand. Worth a try, at least for me, but I have NO plans to dump my Volkls... EVER!!
If you need to get a little relief with this racquet, consider adding some weight to the handle to get a little more HL balance with it. I've never had a racquet feel more sluggish after adding lead to a handle even though it becomes heavier overall like that. My heaviest "trainers" are 13.4 oz. mids, which took over a half-ounce of lead tape on their handles to get them much more maneuverable and playable for my needs.
The first string I'll try in this denser layout will likely be a 17 ga. syn. gut. I have both some Kirschbaum and Prince w/Duraflex. Since I was okay with a bed of poly, I'll do fine with skinny syn. gut at the right tension for sure.