Going to a "lower tier" school isn't necessarily going to hold you back in achieving your career goals (just like going to a big name school doesn't guarantee them), but the thing to think about is why certain schools are deemed "lower tier." Often times it is based on resources and opportunities available to students, as well as the success of its graduates and the faculty. These all factor into how likely you will be to achieve your goals, but doesn't necessarily mean you won't if you can overcome the limitations of these programs.
But instead of applying to lower tier schools (and I agree with others that UNLV is not necessarily lower tier), I would suggest taking an honest look at your application. Are your grades competitive? How much fieldwork/lab experience do you have? Do you have experience in the area (region/theory/method) in which you propose to do your dissertation work? Are the schools you are applying to a good fit with what you are proposing in your statement of purpose? Do you have a firm grasp on the current thinking regarding your research interests and questions and have you clearly conveyed them in your SOP?
If you don't already have a master's degree, I would considering going to a master's only program first and use that as a stepping stone for getting into a top program. I know a lot of people who have done this (many are now in TT positions) and it really can make a difference.