Im a shaman myself. Based on the damage profile of dungeons, do we need more defensives? Yes. Specifically, we need a short small CD defensive for the small but numerous little things. This short CD can be more HP, more armor, a shield, some Ignore Pain mechanic. Something.
1 big massive 60% DR wall for 12s (best wall in the game, better than tanks wall may I remind you) sometimes cant cut it. And using the best interrupt in the game sometimes cant cut it to run smoothly through some mechanics.
That is “shamans need defs” with specificity. With a bit of detail.
What does that have to do with mages though? Why do we need to nerf mages to feel better about ourselves? A shaman is a shaman, a mage is a mage. Nerfing mages wont change the fact that Shamans are squishy.
So YES. Mages are fine.
OK. Name that mechanic. Maybe… dunno… the bleed of the 1st boss of DHT ? So they can remove it once every 2 minutes when the mechanic happens every 20s or so…
Thats hardly cheesing IMO.
In fact, on THAT boss, I bait the cat leaps. Why? Earth shield (-6% DR), MASSIVE vers DR (shaman stacks vers), Mail Armour AND a shield (as much armor as plate DD)… I heal myself back up with 1 riptide. Instant and EZ.
No deff CD rotation, no Aug cauterize, no nothing… 
THAT is cheesing… 
Or maybe the neddles of the 1st boss of WM? I can see WHO will get it on my party frames. Pre-cast earth shield on him for -6% DR and +100% extra healing. 1s prior pre-cast Healing Surge. Dude gets needles, surge lands and instant riptide. DONE.
If the DD wants to help out a bit, a short CD deff is fine. If he gets double hit by casts (highly unlikely but possible) then use pot+wall. But every class has this wall (even shamans) and many classes have a short def CD (ignore pain style).
Thats the only moment where its UFF to heal that. So mage have a wall for that. So do shamans. 