I donīt feel that itīs unsatisfying to see Tanya succeed. After all, her knowledge about history IS her greatest trump card. Greatly enjoyed this episode. It definitely felt like this victory set in motion a true change in history. Should be exciting from here on out.
Btw. something I just now really noticed: You know when in other anime the hero appears and the music gets triumphant in a positive, hopeful way? Well, in this anime, when Tanya and her squad appear, the music actually becomes freaking sinister! Itīs typical "oh no, the boss enemy is about to win, what can we do?!"-music, except here itīs used to mark the victory for the "hero". I found that quite amusing ;D