Take a look at the Simple Rating System (SRS) for the top 4 teams in each conference.
2016-2017
East ... 3.65, 2.87, 2.25, 1.36
West ... 11.35, 7.13, 5.84, 4.42
2015-2016
East ... 5.45, 4.08, 3.49, 2.84
West ... 10.38, 10.28, 7.09, 4.13
2014-2015
East ... 4.75, 4.08, 2.54, 2.45
West ... 10.01, 6.80, 6.34, 4.41
2013-2014
East ... 4.15, 3.63, 2.55, 1.20
West ... 8.00, 7.27, 6.66, 5.15
2012-2013
East ... 7.03, 3.73, 3.35, 1.25
West ... 9.15, 6.67, 6.43, 5.37
2011-2012
East ... 7.43, 5.72, 3.59, 2.67
West ... 7.28, 6.44, 3.16, 2.82
2010-2011
East ... 6.76, 6.53, 4.92, 4.83
West ... 6.01, 5.86, 4.81, 4.41
2009-2010
East ... 7.12, 6.17, 4.44, 3.37
West ... 5.33, 5.07, 4.78, 4.67
2008-2009
East ... 8.68, 7.44, 6.48, 1.70
West ... 7.11, 5.00, 3.73, 3.36
2007-2008
East ... 9.30, 6.67, 4.79, 2.47
West ... 7.34, 6.86, 5.46, 5.14
2006-2007
East ... 4.52, 3.69, 3.33, 0.61
West ... 8.35, 7.28, 7.28, 5.04
I think these numbers are a lot more valuable than simple win percentage because the Simple Rating System takes into account point differential and strength of schedule.
It becomes clear looking at these numbers that the imbalance has been severe since at least 2012.
There were a few years in the 2008-2011 range where the East had several strong teams, notably the Celts, Cavs, and Magic. In those same years, the depth of quality teams (2.5-4 SRS) was better in the West, whereas the East tended to be shallow.
Prior to that, going back to 2007, you can see that the tail end of another period of deep conference imbalance. That was an especially bad year.
Overall, I just don't see the value in even a single season of this kind of imbalance.