WoTA does have a sport weight, maybe that's what you've got? I thought it was comparable to other worsteds though. The Merino is supposed to be dk, but it looked like the WoTA worsted to me. I guess merino squishes down a lot to a dk gauge, but you can knit it at a worsted and it's fine.
Another thing I've noticed about worsteds is that they're thinner than worsted weight from the 70s and 80s. Sometimes they're a lot thinner, and the older yarn is more like what we call 'aran' now - a heavy worsted. The gauges on the old labels are 16 sts/4" compared to 20 sts now, both on size 8s.
sue- knitting heretic