I agree. What I'm saying is that he doesn't fight at all while insensate (except perhaps the dart, as previously mentioned, I don't recall that at all). Therefore, if the emotion blast is stunning to an even somewhat comparable degree (a huge "if", it's almost certainly not, though I do still think it is somewhat stunning), that would be the only chance I could think of.
I think certain people probably would be literally paralyzed, if you've ever heard someone with really bad depression that manifests as apathy, it sounds like it can feel literally paralyzing. I don't have depression, but I do experience intense apathy from time to time, and the lack of desire to do anything is insane and hard to describe. Now, if I was in a life/death situation, it would likely be different, but I'm just using this as an example of real "paralysis" that is similar to an emotion blast.
that said, this strategy is very much not guaranteed to work, I just think it is more likely to work than most strategies. even if it has a 1% chance of success, attacking the Herald head-on probably has less than that, which would make this a better strategy. Far from perfect, but it has a chance.
I think there are a few amplifiers to consider when talking about emotional Allomancy vs heralds.
1) years of torture
2) levels of investiture
personally, I think that years of torture that opened up cracks in their psyche that were so bad that in some cases they were known for something beforehand and are the exact opposite now (Kalak with decision/indecision) make it a higher chance of them getting stunned. There is an argument to be made from the opposite POV that they would be less susceptible, but I don't think it holds water. based on the Heralds holding out for much longer between the early desolations than the late ones, I think it's safe to say that the thousands of years of torture didn't build their mental fortitude, it weakened it.
as for the levels of investiture, you're right. I will note that Brandon doesn't explicitly say that it's the Investiture that's causing it rather than an inherent property of Breaths specifically, but that's being nitpicky, and his meaning seems clear to me. The question then is if the investiture is enough to nullify the years of torture and the inherent strength of duralumin emotional Allomancy, and I'm not convinced it is. I think it could go either way.
Full stop, if it's Taln that we're trying to kill, I think we already lost. I personally think that he would be largely immune to the stunning effects of emotion blasts (due to his proven mental fortitude) and his fighting prowess outmatches anyone in the cosmere. if it's basically any of the other heralds (with the exception of Nale and Kal who require a different strategy all together), I think it's a much better chance. I think emotion blasts would be the most effective on Chana, as she was tortured most recently besides Taln, but I don't think it would make a major difference.
thinking about it, it could be that they have a loosely fixed location, but one that changed based on a variety of variables (rotation and revolution of both Roshar and Braize, among others), but that seems unlikely to me. I feel confident there's some sort of system, but not one that is easy (or even possible) to deduce without Shard-level intelligence.