To be fair, spell speed isn't all that bad for Summoner, not as high a weight as for BLM but it still has a positive benefit on the dots and squeezing in more Ruin III's in Dreadwyrm.

Least as far as 3.0x weights as DET / SPS weights it came down to personal preference on SMN.

Though I do wonder how much the weights have changed with the addition of direct hit into the mix.