Four minutes before halftime Brockie made it 2-0 with a firm, low strike, then completed his hat-trick in the 60th minute with another low drive.
Academy player Tom Biss added the fifth goal in stoppage time, after Brockie nodded on a long throw in.
Shillong's goals came in the second half when the Phoenix made a number of changes.
A defensive mix up allowed Friday Gbeneme to slip the ball into an empty net and the same player added the second 10 minutes later.
A beaming Brockie said the last time he scored four goals in a game was "probably in the under-10s".
"It was a good day because you always enjoy it when you are scoring goals," Brockie said.
"The main thing is that the combinations are starting to work and the more we work and train the better it will become.
"The conditions weren't easy today because the pitch was rough and the temperature must have been in the high 30s.
"That is two strong efforts we've put together and we can build on it."
Herbert agreed with Brockie's assessment of the pitch, calling it "an incredibly difficult surface".
"It was another solid performance on a pitch that didn't help the fluency of our passing, and I couldn't fault the work-rate and commitment that led to five quality goals," Herbert said.
"After the first game on tour (a 3-0 win over United Sikkim on Friday) we had all the squad out training the following day because that is part of our physical programme.
"There is some fatigue there but you will always encounter that at top level."
The Phoenix move on to Shillong today (mon) where they will play an I-League selection in a friendly on Wednesday before taking on either URO United Sikkim or Shillong Lajong in the final of the North East Super Series on Saturday.