I both agree and disagree. Maybe you won't get a million subs from these forums, but I have so far managed to get a few readers in a months time, and it was because of promo threads. Though perhaps not single promo threads like this one but going into the other general promo threads, I have both gotten readers and found comics I have enjoyed myself. I do agree that reaching out outside of Tapas is a good idea, but checking out some of the promo thread's here, promoting your comic, and checking out others will provide some benefit.
As for the topic, I have read your comic and have subscribed. I found it quite funny but only the strips having to do with thievery. The more general strips, I didn't find that funny, so my suggestion is you stick with the topic of thieves and make material based on that.
I also have a comedy comic but my comic happens to have character development as well. Perhaps you can also provide some character development and maybe even some story lines. Since this is about thieves, some capers would be fun to read.