This has following reasons:
GS is tied to Weapon speed now so you can't attack that fast anymore.
Phase run which was a heavy damage booster doesn't exist anymore.
The common RT build as Mara isn't half as effective anymore.
For example I am experiementing with Sweep,FT and Molten Shell as dps cannon. This works quiet fine damage wise but I wish the Mara had some AoE nodes at the beginning because I am a glasscannon with such builds only abusing the poor Monster AI. I think I needed 46 minutes for Merveil, while a similar Templar build needs 40-42 minutes.
The main weakness of the mara is that the build isn-'t one simple line such as other classes and you have to fork.
Marabuilds are heavily depending on weapons now.
For example I chanced this beast at cavern of anger, which made the forest and rivercossing a oneshot paradise.
But I lost the first mara rank the last reset because I found the first big pack 10 seconds before the end.
Maras simply miss the "ready to rock node" or another level 10 gem quest.
Templars got amplify and WED.
Witches got AoE
Duelist attack speed and master of the arena.
Shadow Acceleration and crit.
Rangers attackspeed and movementspeed.