Sebastian Larsson opened the scoring with a long-range effort before two quick breaks on the counterattack led to the second and third goals from Johnson himself and James McClean respectively.
"I think that was the best we've played this season." the winger told the Daily Mirror. "We looked threatening and cut them open so many times – everything clicked for us.
"The team played higher up the pitch and it gave the attackers more chances. And then we didn't have as much space to cover getting back and forward."
The 25-year-old appreciates his place in the team after his time at Manchester City, and he credited manager Martin O'Neill's decision to name a settled line-up in recent matches with their improvement.
|11/2||Sunderland are 11/2 with Bet365 to draw 1-1 away to Wigan on Saturday|
"I think at Man City once you start coming on as a sub, you do get classed as a bit of an impact player even when that's probably not even true. It is nice to be playing week in, week out.
"I think I've started more games for Sunderland probably than I did in the whole of last season. I think that tells you the story. My game is definitely benefiting from that. I feel much better - physically.
"We're nearer the top half than the bottom three now and I think that shows the improvement in recent weeks. We beat City, we got a good win away at Southampton and I think things have picked up overall from earlier on in the season."
O'Neill himself stated that the Black Cats' three different goal-scorers on Saturday showed the diminishing reliance on Steven Fletcher, who scored most of the Sunderland's goals in the opening stages of the season.
"In the early part of the season if Steven Fletcher didn't get a goal you were wondering where one was going to come from," he added.
"But now other people have chipped in and that was nice. It is a good confidence booster."