I absolutely agree that Momentum is well worth it as far as Talents go. It takes 3 ranks in order to have the CD in sync with RoF thus allowing a constant rotational spam of the two AoEs. I use this with doubles in WB and my per round gold income on Voucher buff increased by around 10-15k immediately. You will run into rage issues spamming it anywhere other than GB battles ( I'm in PvE gear with about 37 starting rage so no double casting on start of the fight). I can tell you that the healing chance is extremely low (probably below 1%) since I've had the Talent for quite a while and only noticed it proc a few times.

Survival - I have 3 ranks of this Talent as well and what I have noticed is that at Rank 3 and later you start to run into issues in MPs unless you have a second mage. Even with DF on the boss I tend to be about 3-5 seconds behind most Bosses on their large damage single target attacks after my first casting. This can be disastrous if DF or IS happens to wear off at the wrong time due to any number of factors since a lot of the level 70+ bosses will drop the tank shortly after their single target attack if healing isn't quick to show up. A good tank and archer obviously mitigate these factors but I'm hesitant to go much farther than 3 ranks on this Talent because of this. The big bonus on Resto that people forget is the % damage reduction buff. The longer you can keep this buff up on the tank the better so a longer CD on Resto means MORE time in between on this buff.