That would be a reasonable suggestion for candidates for the House of Representatives, but it still wouldn't have changed anything for Cruz, who's a Senator, as those seats are allocated directly based on the state boundaries.
If anything though, Cruz's constituency is overly large, meaning that he represents more people, and therefore likely had more raw votes, than most of his Senate counterparts - Texas's population is somewhere on the order of 25-26 million, easily more than the 10 least populous states. In the 2012 election, he received 4.4 million votes out of about 7.8 million or so
Overall though, the Senate is grossly disproportionate in a lot of ways. Large states like Texas are grossly underrepresented, not only because all those people who voted for him don't have the same influence as a state less than 10% the population of Texas, but also because the number of people who voted for his Democratic opponent alone (3.1 million), nevermind 3rd party candidates, is larger than the full population of something like 20 states, and larger than the average number of Senate votes in many more than that. Those people get absolutely zero representation in the Senate.
To illustrate just how far off it can get, the 26 least populous states have somewhere around 56 million residents (source http://en.wikipedia.org/wiki/List_of_U.S._states_and_territories_by_population). You could elect a Senate majority with half that, and if we go by the national voter turnout rate from the 2014 election of 36.3%, and not considering how many of those individuals are ineligible to vote (due to citizenship status, age, etc) you'd only need about 10 million votes, in a country of roughly 320 million people to have full control of the Senate.
Now, that's a bit of an extreme example, and it discounts that some of those smaller states lean left (VT, DE, RI) while others lean right (WY, AK, ND/SD), just as the same is true for some of the very populous states (CA, TX), but it serves to illustrate just how skewed and disproportionate the Senate can be in terms of representation.