I dont want to sound like I'm badgering you because I'm not. I like talking resto shammy alot especially with someone that is backing their opinions up like you are. However the OP was talking about the Drak fight where his tank was getting gimped and he had a rogue pulling adds. With that setup gearing for single target IWS healing isnt going to work IMO.
As I've said in actual Raids there isnt too many fights (none that i can think of) where I cant main tank heal with actual resto shaman gear and ES RT and CH (with the occasional HW if things get rough). It's not that i dont enjoy it or the idea of doing it, its just that shammies are so good at raid healing that its like making a geared up rogue spec and use his ranged attack and having a hunter melee because he geared up for it...you can do it but that doesnt mean your not making things harder than they need to be.
As for not trying it and your gear not working: although i cannot see your gear i would have to admit if you are in ele gear, you are right you probably do not have the mana pool or mp5 to do it. Hopefully you have at least picked up some of the CH totems that dropped, that can help in trying it out. As for the final thing about the LHW i have a totem and a very strong naxx and os ele set i might throw on just to change things up when we are out gearing a raid. its something to have fun with but in progression yes im stuck on the idea that resto shammies should be doing what they can bring to the table better than anyone else.