Stat development wand vs. staff level 50 to level 75

Introduction
As a follow up to my first intelligence gear stat thread I wondered about something I read in one of WhoIsThis' rebalance threads: Are end game staff sets really getting worse compared to their wand counterparts or is it just the missing armor that is keeping mages from using them?
The basic idea is pretty simple: With a staff set you trade in survivability for superior damage. I compared sets from level 50 to level 75 to see if it is a fair trade for every level. One disclaimer: At level 50 I compared different sets - Shadow wand set und Keeper Cosmos set. I find the Shadow staff set inferior to the Keeper set and think that the Keeper's Enchantress set was and is the best available level 50 staff set.

The graphs show the staff set compared to the corresponding wand set.

Offense stats
Attachment 48713

While there is no steady development recognizable this graph shows another odd fact about the Enchanted set: The staff variant has a higher crit than the wand set. This actually makes sense as using staff means focusing on your damage output - it's just highly unusual to see.

Defense stats
Attachment 48717

The dodge decrease for staff sets seems to be stopped since Humania. The Fiery staff set has a very low health regeneration and Enchanted once has odd stats: The mana regeneration with staff is higher than with wand. This is perfect to spam your damaging skills. :)

Heal and skill damage
Attachment 48722

Now that is clearly one recognizable graph. In comparison with the respective wand sets heal and skill damage have been going down since level 50. This means that the main reason to use a staff set has been vanishing slowly from expansion to expansion. And on a side note heal with staff is always lower than heal with wand.

Conclusion
It's right, staff sets are getting worse. Especially the drop in skill damage is dramatic as that is the main reason to chose a staff instead of a wand set. In comparison once again Enchanted is an exceptional set as the staff set seems to be superior to the wand set in many aspects.
But in the end there is hope for staff prefering mages: In the last graph the skill damage lines go slightly up from Sand Goddess to Fiery. And the Fiery numbers are with the set staff - using the level 76 elite staff shows an additional increase in armor, dodge and damage. So using the staff set isn't as attractive as it once was but the low seems to be behind us.