There is an off-peak season for travel to Hawai'i that takes place in usually Oct and April, as well as February. The off-peak season does vary. I think it'd be best, though, to go in April. You might encounter April showers, but you take that chance almost anytime you go during non-Summer months. Spring break officials lands in the third or last week of March according to the DOE and you have schools getting out in May, especially UH.
The first class ticket sales you were referring to, the ones that costed around $1200, were part of a discounted First class fare intiated by American, Delta and Northwest. American and Northwest have pulled that fare, but Delta still has it. My guess is that it's not coming back for those two carriers, unfortunately. (Though the market might warrant cheaper F fares and I could be wrong, and am hoping so)
aloha