A day in the life of ..

[MongoJerry]

But weaving stacks 5 times - every time you add a flay or a blast, you'll get another 3% from weaving, and I was under the impression that each one lasts 15 second (i.e., they unstack sequentially instead of all at once).  So as long as you're hitting with shadow spells, some amount of weaving should be active at all times.

They unstack all at once, but every time you hit a mob with a shadow spell, you reset the 15 second timer, so that's to your benefit. Sometimes in raids, I'll "pump" shadow weaving by casting four level 1 SW:Pains and then a full rank SW:Pain to get Shadow Weaving up to 5 times to benefit the warlocks and other priests in the raid. Then, I heal for a little, cast another SW:Pain, heal a little, etc.

For my part, I haven't seen much benefit from Improved Mind Blast, because Mind Flay is so good. With two points in Improved Mind Blast, I can perfectly fit in two Mind Flays in between each Mind Blast. When I had more points in it, I always had to stop mid Mind Flay to take advantage of the faster cooldown. It didn't seem worth it, and I've liked spending the saved points in Shadow Focus.

My current shadow priest build, which is heavily PvP-centered but also is used in large raids is as follows:

Neriad's shadow priest build

The main problem with this build is the reduced mana supply and efficiency when healing. I make up for it with good gear and lots of mana pots and nightdragon's breath.