the lines in the arches are not smooth and neither is the weld - get your denter to buff this entire panel with a brush or a brass/horsehair combo brush so you can actually see the metal you are working with.
The reason for the rust that happens here in nearly all the E70 corollas is poor water sealing in the wheel wells and poor application of cavity wax inside the body panels.
You will need to treat the body inside otherwise these panels will rust 100% faster than the original metal.