I am pretty new to HD (maybe 3 seasons). I am noticing that my teams get destroyed in the second half, we would build a 14 point lead then get outscored by almost 20 in the second half. I have tried switching up tempos but i still dont get it. Is there a good mix of tempos that would allow my team to keep up good play?

I found three games that followed that pattern for your Roanoke team (losses to W&J, VW and E. Mennonite)...in two of the three, I'd say fatigue played a role in the second half as you have yellows and oranges playing opposite your opponent's green and blue in the second half, that will lead to more turnovers for you, more fouls for you (and FT scoring attempts for your opponent) and a less-effective defense, which will improve your opponent's shooting percentage. The IQ's (your Def. IQ vs. opponent's Off. IQ, specifically) might also come into play...most of the teams that have sprung back after the half have been teams fairly loaded with A- or better ratings. 

Biggest suggestion though would be to go back and look at the boxes and see which players are getting fatigued and the approximate point those guys are starting to hit yellow and then tweak the substitution pattern enough to spell those players from 3-4 minutes so that they don't get quite as fatigued. 

Take a look through the play-by-play of each game.  A quick scan of the fatigue colors of your players and the halftime defense adjustment by your opponents will do.
You'll probably notice your players going yellow & orange while your opponent's fatigue colors are green & yellow; that's a big problem.  Also, your opponent's halftime adjustment will be +/- 2 from the 1st half setting and may be doing a very good job of taking away either your interior game or perimeter game.

You probably need to limit some player's minutes (adjust the fatigue settings to no more than getting tired); slow the tempo one notch from what you'd like to run; and check to see whether you can make a gameplan adjustment to take advantage of your opponent's overplay.  For instance, assuming you're try to score down low exclusively, play slowdown, with everyone on fairly fresh, and find someone (even off the bench) to jack up treys to take advantage of your opponent's defense sagging down to the paint.

Thanks guys, i see now, my players are dogged while the other team has a lineup full of fresh players. While doing my depth chart i use "target minutes". From what you have seen, which benefits more, "target minutes" or "fatigue"?

I'd only use target minutes if I had a bunch of freshmen on the 2nd team.  Typically, your starters get more playing time with 'target minutes' but they'll be playing fatigued more.

With 'fatigue' setting, they come out when they are tired. 

I prefer 'fatigue' settings, set to 'fairly fresh'. If my starter is much better than the sub, I may put him at 'getting tired'