In 2014 there were 486,651 apprehensions on the border, in 2015 this dropped to 337,117 and rose back to 415,816 last year.
Source.
Just by correlation I would say that the violent encounters were bound to go down as such in reflection of the lowered overall numbers, whereas the amount of attacks on officers slightly increased.
I see this as a "success" in the vein of the "failure" that was the introduction of metal helmets in ww1 which increased the reported head injuries, took them a while to realize the helmets were merely converting fatalities into injury.
The cato instutute is a libertarian think tank funded by the koch brothers, without supporting evidence It would be hard to take take their words as mcuh more than biased allegation.
Speaking of libertarians, going a bit further back it can be found that it was obama of all people who was wrestling with the republicans into underfunding border security.
House GOP slashed Obama's $3.7 billion into $600 million on an emergency bill in 2014.
I'm looking for whether this bill passed so low but if it or any other gutted bill passed it might explain the why of the lowered apprehensions.