He's not immaculate with technique or angles, but no one really is. I didn't really feel like it was a problem.
If he's not learned to tackle after 4 years of high school football and 4 years of college ball, he's not likely to become a great tackler now, though as with Heath, Richard may be able to improve him some.
But regardless, unless the Cowboys can move up appreciably in the draft, I doubt one no. 58 pick isn't going to make a huge difference in the defense. In my experience there's really only about 50 really good players in any draft, there are exceptions but after the first 50 you're into the second tier of players, and unless one of your defensive starters (say Heath, for example, I'm not as down on him as most it seems but we'll assume for the sake of argument he's the "worst" defensive starter) is notably worse than a late second round rookie, you're not helping yourself that much
this year. A close comparison might be Darren Woodson, but even he was picked 37th, inside the top 50, so in my evaluation he was a really good player, but he did little his first 2 years, though the defense was already pretty good in 1992 so as a rookie he wasn't better than Everett, who was a 5 year vet in 1992.
Can't see the Cowboys coaches throwing Savage into a starting role his first year, either.
Just saying don't get too excited about any player picked at 58, you're likely to be disappointed...