However:
Employers will have to hire fewer workers because their workers are more productive
More people will be interested in the jobs, increasing employee competition
Since people vary, some people's increase in productivity will be insufficient to cover the increase of wages
The end result it seems is that getting a job is made harder. This is not to say that increased wages are bad, they are great.
"increase in productivity will be insufficient to cover the increase of wages" is only true if the company isn't turning a profit or paying high salary to managers. This is relevant for some small businesses and bankruptcy-threatened large business, but not for the largest players in the economy, like Walmart.
2) Whether the company is turning or a profit or paying a high salary is completely irreleavent. The question is whether or not you are productive enough that hiring you makes the company more money then they pay you.
Efficiency wage theory definitely doesn't assume that. In fact, a big part of the theory revolves around your existing workers becoming more productive.
Even if you assume your applicant pool stays the same, you would see less turnover with efficient wages—and hence fewer job openings.
This assumes that workers are of a fixed quality. I know I worked harder for $10/hour than I did for $7.25. Higher pay means stronger incentives to do well and less stress from poverty.