It is all in the headline. Tactic training.

"Does anyone no (sic) better place to do tactic trainer?"

With unlimited Tactics Trainer problem use that comes with your Diamond, how could you want more / better? 

If you're not satisfied with chess.com's tactics trainer, then try this:

www.chesstempo.com

It's free and I like it very much.

Know.  Chess.com is the best!

ChessTempo.com is much better than tactics training here though I subscribe to chess.com for other things (I should really take more advantage of chess mentor).

You have to admit the chesstempo.com does have a much better tactics trainer, with more options and ways to train. No offence to chess.com though. Both are great sites.