No...just no. You already have one of the strongest single target healing spells in the game. There is absolutly NO need to buff it further. If you really want to to overcharge a heal, for example Riptide, you can use Unleash life w/o having to waste 3 Skillpoints. (Unleash+Riptide is a pretty strong combo, but doesnt work on molten right now).
UL nor Focused Insight are really a gain before the tank dropped below 20% because all you would achieve would be a massive Overheal.
So lets say he did drop on 15% HP
Naturally you want to get him up as fast as possible.
1) Riptide
2)1sec GCD
3)You shock the Boss
4)1sec GCD
5) Unleash Life
6.) 1sec GCD
7.) GHW ~1.5sec cast time
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By now 4.5 seconds passed and your tank is already dead. GJ wiping you raid.
Shocking is simply not worth it. Wasting a GCD...just no.
If this doesnt convince you all I can do is some math.
Focused Insight: +30% Heal
Unleash Life : +20%
Makkes a 50% Heal increase
Let's say you heal with about 30k.
If you charge your heal with FI and UL:
30,000*1.5=45000
You just healed 45k in 4,5 seconds. Thats 10k HPS.
Now lets see what else you can do in 4.5 seconds
1) Riptide
2)1sec GCD
3) GWH ~1.5 cast time
4) GWH ~1.5 cast time
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All in all 4 seconds
Take our example from before: 30k healing output with GWH.
30,000+30,000=60,000 in 4 seconds which equals 15000 HPS
Congratulations. By NOT using Focused Insight and Unleash Life you healed 33% more in 90% of the used time equaling a 50% Heal Increase.
And if you say: Well you could only charge your heal with Focused Insight and not with UL to save time: WHY SKILL IT IN THE FIRST PLACE?
And about the "Oh, but I save mana and it gives my heal an increased heal/mana ratio.
You have a BASE mana of 23430 as a shaman.
GWH cost 26.9%
UL cost 8.2%
Flame S cost 11.9%
Frost S cost 21.%
Earth S cost 14.4%
Wind S cost 9.4%
Riptide cost 16.0%
Now assuming you use Wind Shear because it's the cheapsest of your shocks:
Riptide+UL+WS+GWH cost= 60,5% of your BASE mana = 9454 mana in 4.5 secs= 2101 mana/sec
Riptide+GWH+GWH cost = 69,8% of your BASE mana = 16354 mana in 4 secs = 4089 mana/sec
Some of you may SCREAM in anger right now and think: " SEE, I TOLD YOU: WE SAVED 6900 MANA!!!1111"
BUT you forgot that you have healed only 45k while I healed 60k and regenerated 0,5 sec mana (in Combat 300)
So lets math this up
45,000/9454=4,8 heal/mana
60,000/16054=3,7 heal/mana
Gratz, you saved 30% mana consumption while loosing 33% heal.
Conclusion: You spend less mana and more time for a healing combination that dishes out less heal? No, no thank you.