I haven't played my sham for a while, so I'm a bit out of practice, too.
I usually play pug (wb and sc), but lately have been roaming with one or two guildies.
In wbs I try to keep up my hots, and quickly rez via instarez. Rather rarly using the grp-heal.(grp-heal spam is kind of boring and makes more sense on other classes imo

The most problems I have in SCs and while roaming. I find it very hard to compensate bursts, as I can't do much more than apply hots, shield and maybe the (expensiv) small st-heal. Atm I can't make the lifetap work for me, even with reduced casttime.
So any tips on utilizing the sham as a healer are welcome