The added slow only increases up to 65% (at least the tooltip value). I suggest increasing this to 70% (+2% per level of skill rather than +1% and starting at 62% rather than 61%) Or changing the morphed effect.
If you also want to look at comparisons between this skill and the Warden's Permafrost Skill, Permafrost has no synergy requirement, and stuns for 3 seconds rather than 2.5