Yeah I wouldn't even look at ERA when evaluating the lab. I'd look more at FIP, SIERA, and K-BB% as those are better indicators of purely the pitcher.
Here's an example of lab success.
Before Milwaukee - 5.74 FIP, 4.90 SIERA, 7.1 K-BB%
In Milwaukee - 3.42 FIP, 3.16 SIERA, 19.3 K-BB%
After Milwaukee - 3.39 FIP, 3.78 SIERA, 12.6 K-BB%