That thread talks a lot about forked darkness. There are Four problems I have with Forked Darkness.
1 DoT buffs should be in Madness, not lightning
2 You can not get both Forked Darkness and Wrath, which would make it useful
3 The proc chance and damage buff are both too low, especially for a T7, it basically requires force Nexus to be useful
4 There are already too many abilities chained together in lightning, why one more.
Simple solution, place the Thundering Blast portion in Forked lightning, and switch Forked Darkness with Focal Lightning, as Lightning is the tree that could benefit more from Alacrity anyways.
You are on spot on your observations i hope some developer notices it, have you posted on the PTS thread?