I am a high elf, vampire, mag sorc with no pets. I use Undaunted Infiltrator and Infallible Aether/Mage sets and usually Grothdar like the Easy Mode Sorc guy. I don't have Maelstrom lightning staff yet, but when I do, my lightning staff heavy attacks will be very powerful. They already are even without the Maelstrom staff. I realize this doesn't answer your question about what's happening post-patch, but my point is that if you choose the right gear, CPs, mundus etc. you can maximize everything for powerful heavy attacks and I doubt that will change post patch, even if it's nerfed in some way I doubt it will be significant.