Even the most powerful thaumaturgist can only call as much power as his conviction in an exchange - there isn't a way to boost thaumaturgy's power, only its complexity.
Power is controlled with Discipline not conviction. (YS262)
And thaumaturgy attacks don't have weapon rating - they're just attack rolls.
Think you have this backwards - the spell's complexity has to account for the victim's resistance and any other obstructions. In other words, it's all "weapon rating" - the rolls are just to see if you screw up and can be spread out over time.
Now, compare with a feet-in-the-water focused practitioner with Conviction 4, Discipline 4 and a +2 control focus, pretty much the weakest evocation-based caster you can build that's actually focused on his magic. He gets +6 attack roll (the absolute best a thaumaturgist would ever get) and also gets a weapon rating 4. The weakest evocation-user can deal 4 more stress than the strongest thaumaturgy user... and the thaumaturgy user still needs sympathetic links if he wants to directly affect people. As for what a really powerful evocation-focused caster could do in a round... I'm currently playing a pretty strong warlock. She can do Weapon 16, Attack +16 spells as rotes. If she really pushes it, she could level a dozen skyscrapers in one blow or rip apart a small army.
One of the more...broken...builds is a thaumaturgist, specifically a potion crafter. You can hit double Lore plus focus...not going to match the addition of dice an evoker gets on a good roll but also won't have the bad rolls affecting power.
Because it still is a strong spell for a rushed thaumaturgy and it takes 3 exchanges to control the power. When we're talking about one-round thaumaturgies, we mean 3-4 shifts for most casters.
Ok - you're still (usually) going to need to set up a symbolic link. Assuming you can do so in one round (questionable) you could cast a weak spell every other round...so weak it's easily resisted.
No you don't. Someone with Conviction 5, Lore 5, Discipline 4 who has a +2 control for a certain type of thaumaturgy will roll control at +6. When casting a 5-shift spell -- and offensively that's an attack roll of 5 with a weapon rating of 0 -- he will fail his control roll 1 time out of 3. So he either takes backlash (stress) or the spell goes to fallout, which can still cause him stress. Only powerful casters could ever cast rushed thaumaturgy without stress... and it would still be inferior to other powers or weapons (or even unarmed attacks) in direct combat.
Eh...don't push it and keep a tag in your pocket for bad rolls. Both evokers and thaumaturgists should do so! They have the same issue after all.
A careful thaumaturgist won't need to take stress from casting. Just have a
Focused Mind and a
Memorized Ritual (Discipline and Lore Declarations) ready to go at need. (Best to be a bit more creative with declarations but hey - it's late!
)
Symbolic links are, of course, still needed.
Yes - addressed this earlier...and below to a degree.
All of the above combined means that, while you can do combat thaumaturgies, such types of spells are impractical. A martial artist will be hitting harder in combat than a thaumaturgist, will run no risk to take stress, and doesn't need a sympathetic link to harm the target.
I pretty much agree with you here...just not convinced the symbolic links are practical to set up at combat speeds. I think we agree on the result - just differ on a few details.
The normal symbolic links for opening a way, veils, healing, conjurations and illusions are the targets themselves.
Unless you have the target itself with you, you need a representative symbol to target with thaumaturgy.
"In order to affect a target at great range (whether in physical distance or some other dimension), some sort of link must be established to that target via symbolic representations, the incorporation of recently-separated bits of the target (blood, hair, a family keepsake), and so on. Without these physical materials on hand to represent the target in absentia—as well as for anchoring
the purpose of the spell to the ritual—a thaumaturgic spell simply has nowhere to go and nothing to do." (YS261)
Having the target(s) at hand get's around the requirement if you only needed one target. Elaine's Reiki Healing Spell is an example.