To address the request a bit better than just saying "Renew is now just a heal over time (hot) to buffer Tank damage and Empowered Renew is a poor way to spend 3 talent points", lets first look at how the non-Empowered Renew is best used and then see why Empowered Renew isn't as empowering as it seems.
I'd like to hear more about empowered renew. I was not using it
much pre 3.1, but was thinking the upfront instant heal would make it a bit more
Usage of non-Empowered Renew:
Renew has been predominantly used a pre-hot to keep up on someone taking consistent damage (ie: Tank) or on someone who's about to take damage. The limitations of the spell are such that it a) costs a decent chunk of mana b) requires a long period of time to apply the full healing and c) limits the amount of time one can stay oo5SR if they use it as a pre-hot on multiple teammates. Understandably, Renew becomes less efficient if it doesn't provide it's full healing.
Of course, you knew that already.
So where does Renew fit?
Unfortunately, the answer is: Pretty much only on the Tanks.
The reality of raid healing in many raids is that hots on non-Tanks never tick to full because healers would rather spend mana to top someone off 'now' with additional heals than watch a raider's health bar slowly tick to full over the next 10 seconds. I like to call it 'Healer Anxiety'. Healer Anxiety is a huge issue because it has the potential to waste a raid's mana, through massive overheal and unfortunately, the easy entry level WotLK content has largely encouraged healers to play 'whack-a-mole' in order to boost their healing meters as their healing assignments are usually at zero risk of dying.
Unfortunately, the current raid content is different from pre 3.1 as raid damage comes fast and plentiful, and spending 4.5 seconds and over 1k mana over 3 GCDs to Renew 3 raid targets as a pre-hot becomes largely irrelevant because your next few casts contain Circle of Healing and Prayer of Healing, the Resto Shamans are bombing Chain Heal after Chain Heal and the Resto Druids are mashing Wild Growth, Nourish and pre-hotting with a faster ticking and far more efficient Lifebloom.
The bottom line is that Renew just doesn't cut it for both mana conservation nor raid healing because it takes too long to apply its full effect across multiple targets and the value of the healing ticks that it provides is woefully small in comparison to the amount of incoming damage the raid is receiving; Ulduar raid damage is nothing to sneeze at.
What about Empowered Renew?
Empowered Renew grants a bit more oomph in each of Renew's ticks but more importantly, it turns Renew from a proactive spell to a reactive spell. Understandably, players are now encouraged to use it after teammates have already taken damage. This is good, right?
The main problem with turning Renew into a reactive spell is that it's initial heal doesn't heal enough for the investment of 3 talent points. Effectively, those 3 talent points generate an initial instant heal for a bit more than 1k. While this initial heal is an okay buffer heal so that the rest of the ticks can bring the target towards full health, the ironic aspect of Empowered Renew is that when used reactively on multiple targets, the ticks have even less time to apply effective healing before Healing Anxiety sets in.
As an example, let's compare a Priest that proactively Renews 2 targets before a raid damage occurs and a Priest that reactively uses Empowered Renew. Let's arbitrarily say that the proactive Priest gets 3 ticks from both Renews before Healing Anxiety kicks in and all of the raid damage is caught up. Essentially, by taking Empowered Renew, the Priest is trading a normal Renew tick for the initial heal and subsequent ticks being a bit stronger. This is okay because this is a bit more healing than the proactive Priest would provide on his first Renew. However, if the reactive Priest casts a second Empowered Renew a GCD after applying the first Empowered Renew, the second target actually loses a tick of healing, if compared to a proactive Renew, because there will be less time allotted for the second Empowered Renew to tick before Healing Anxiety kicks in.
In addition, the proactive Priest can provide further healing while the reactive Priest is casting his Empowered Renews.
Ostensibly, the best utilization of Empowered Renew as a raid heal would be to ignore the initial heal and use Empowered Renew as a proactive hot because of the stronger tick. But, the big question for players looking to maximize their builds then becomes, "Is it worth it to spend 3 talent points to get 15% more of your bonus healing effects on a hot that's unlikely to fully tick out?"
For me, that answer is No.
Amusingly, I don't even take Improved Renew for the very same reason.