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Despite doing lot of tactical puzzles my tactical has not improved so much. (I have done over 15000 puzzles during the last 3 years).
Why do I/we not improve only by doing puzzles?
I think that many (weak) players don't have the enough tactical understanding. When doing puzzles they often look at them in a unstructured way, and then tries something which looks good. Often the move is only a best guess at the most promising move. Trying to solve a puzzle fast, without understanding, just strengthen this bad habit.
In order to better at tactics, I have found "Understanding Chess Tactics" to be helpful. Review: http://empiricalrabbit.blogspot.com/2012/02/weteschniks-understanding-chess-tactics.html
Your solution is a sensible one! I believe that the link you recommend is very good!
In addition, I have to say that a good coach could also be very helpful in improving one's tactical understanding!