Treetard I took a look at your WOL report in more detail. I've had the same problem like you, getting blamed that I killed someone so I know where to look
First of all, your total healing on that shaman was 387k, which would increase the tick of the dot for roughly 40k damage and you did not heal him instantly, but over time so no chance that was result of his death.
If you go to the beginning when he received the dot, you will notice that your priest Heaven healed and over healed him for 174k. followed by bloodworm bursting and doing another 41k heals (another over heal), so in total it was 215k healing done to that shaman before the first tick of dot, it also means the starting damage from the dot was not low like usually but it started high, roughly 50k starting tick which is too much to start with.
Your healing was quite effective, and as stated above, not your fault he had high ticks, you did contribute but not your fault.
In addition, he did not die from the dot damage, he died because your warrior failed to interrupt explosion while in his construct, that was the damage that finished him, otherwise he would probably survive. The reason I think he would survive is because he had the dot ticking 160k on him and would have lasted another 10 sec, considering the tick is every 2 sec he can keep him self alive, and healing roughly 1mil in 10 sec shouldn't be a problem for 1 healer.
All in all, your NV contributed to his high damaging dot, but the main fault lies with your priest and DK, and at the end with your warrior who failed to interrupt explosion.
P.S: Reddayspring is correct, the heal while using NV heals in 20 yard range...so tell your shaman to get out of melee :P
EDIT: to get this information go under log browser, add query, in target write the name of your shaman, and also check to see hit and heal. U should get the same information as I did.