I found 2 bugs associated with the Eternal Haunt node in the Wandering Spirits skill tree.
The first is a text bug. Everything seems to be working properly as described by the node as far as making the cooldown longer, however, Eternal haunts adjacent node, Medium, also makes the cooldown longer but in the tooltips Medium has a -% while Eternal Haunt has a +%. Both seem to make the cooldown longer properly and I believe it is a tooltip text bug.
Second is the more pressing matter. Eternal haunt is supposed to make the duration of Wandering Spirits last 10s longer per point. It works for the first point, but further points in it only make the cooldown longer without making it last longer. This is very similar to the Marked for death Desecration node with the first point giving the 5% damage, but nothing further.