It has been my experience that yes, it has been.
I talked to Pyro and he said he didn't see how it would have happened, but I've hit folks on multiple occasions 1 time and not done any significant damage. Hitting near the engine for me usually results in a oil leak, not a dead engine.
It has gone from a 1 hit weapon with 2 hits needed sometimes, to a 2 hit weapon, with 3 or 4 hits needed sometimes. On fighters anyway.
Haven't noticed much of a change vs bombers, but they are usually going so slow and straight that I can aim at the cockpit and hit it.