I absolutely agree. Bill Parcells once said that for every starter you have on your O-Line, you must have a competent backup at each position.
Not 1 backup guard or 1 backup tackle for your entire team (like the Bills tend to do), but one backup LT, LG, C, RG and RT.
To play the devil's advocate here, let's assume Wood can make it back this year and start. With Incognito gone and Simmons a UFA, we don't have any competent backup at either guard spot. So yes, I feel like this is still a huge need.
I honestly hope the Bills sign 1 more FA Guard and 1 more FA tackle with some starting experience. Then when the draft rolls around, take a OT early (1st or 2nd round) and a late round Guard and Center prospect and let training camp sort them out. Only then would I feel comfortable with the depth on the O-Line.