I would think so; getting a LOR from a graduate TA might cause more harm than good, since the schools may wonder what is wrong with you (as an applicant) that prevented you from having ANY science faculty LOR's.
Why are you averse to getting science faculty LOR's? If you don't think you have enough of a personal relationship with any (never went to office hours, etc.) it still doesn't hurt to ask those you think may recognize you. I never met my P-chem professor outside of class (since I work full time and his office hours were during the work day) but when I met with him to ask about a LOR, and explained why I wasn't available for any of his office hours or the seminars he recommended we attend, he immediately offered to write a strong LOR for me based on my class performance. Basically, approach any professors whose classes you did well in, and hopefully they will remember you enough to write a LOR. Good luck.