I do have to admit that compared to Sasuke during his fight with Haku, she has superior abilities with just 1 tomoe.. where he had a 2 tomoe and 1 tomoe combo going on at the time (due to him awakening his sharingan years prior in the massacre and once again in that fight). However, you can also say that she's had it and has been able to use it longer than Sasuke did, which is why it appears as though her abilities are better. She's just had more time to develop it. She was badass against the Shin clones, but they had nothing on Haku in speed.
I do think it's a bit of a reach to give her such strong abilities like what you're saying with just base sharingan. If anything, her speed and processing power will increase with 2 tomoe.. and maybe with 3 tomoe something interesting might happen, but nothing extreme. I mean for all we know she might be with 2 tomoe until the destruction of the Leaf, which will unlock her MS. I mean if her 2 tomoe ends up being what Sasuke's 3 tomoe was in his fight with Naruto.. then there really isn't much of a need for her to get to the the 3 tomoe.. So why not just skip it? Have her be the first Uchiha to unlock MS after just having 2 tomoe. I know that goes against the norm, but her sharingan already is going against the norm lol.