You clearly and demonstrably don't know what you're talking about.
Greater Healing for Cleric is 300.
Cast time on VP Staff is 7 seconds. Recast time is 0 (being a clicky).
Cast time on Torpor is 6 seconds. Recast time is 6 seconds.
Torpor costs 200 mana, VP staff is 0 mana.
If you got super lucky and Torpor landed less than 1 second before a server tick it would take ~23 seconds to heal for 1200 (6 sec cast) + (3 * 6 sec ticks). If you got unlucky and torpor landed right after a server tick it could take up to ~30 secs (6 sec cast) + (4*6 sec ticks). This is of course not taking into consideration potential fizzles (which being a clicky VP staff can't fizzle)
The correct math is:
VP Staff: 300*4=1200 in 28sec for 0 Mana
Torpor: 300*4=1200 in ~23-30sec for 200+ Mana (depending on fizzles)
Plus:
- Sustaining the same amount of healing over a long duration fight with Torpor would require precision timing on recasts, great luck with fizzles, constant Canni spamming (which means you have to heal yourself too) meaning you can't do anything but Torpor + Canni Spam. Where with the VP Staff just requires mindless spamming and no chance of fizzles or need to heal yourself. At any point the cleric can simply not click the staff to cast another spell and only lose a tick or two at most of staff heals.
- You can infinitely spam VP staff and never run out of mana.
- Not having to sit to med nearly as much means fewer chances for sit aggro.
- A shaman can only cast Torpor X number of times (varies depending on mana pool and fizzles) before going OOM and having to Canni, at which time Torpor spam becomes even less efficient.
- You can cast Celestial Elixir (300 mana) and then spam click VP staff and have essentially double the healing of Torpor for only 50% more mana.
- Torpor has snare + melee slow, VP staff does not.
- Being a cleric there are many other tools at your disposal that a shaman doesn't get. Most notably CH, DA/DB, Rez, etc. Really the only utility a shaman has over a cleric for killing high end mobs is Slow, which can be nullified by high MR mobs or simply bad luck with RNG on Slow resists.
I also have the option of dropping a Celestial Elixir for 300 mana and then VP staff spamming to get ~100% more healing than torpor for 50% more mana.
Since VP staff is mana-free and not subject to fizzles. I can duo/trio/small group the same mobs that would require slow + torpor on my shaman to duo/trio/small group without slowing (and having to worry about getting screwed over by RNG with slow resists).