...Is this a reasonable plan?
sinophile888, bear in mind that I and others may not examine every flight that flies within, into or out of Oz...impossible.
That said, you plan is an excellent one provided (as a given) that you perceive OD to be safe. That's the most basic requirement. You will minimise your chances of missing a connection by having two nights in Kuala Lumpur. Many travellers may not be as careful planners, or may be in too much of a rush to allow 36 or 48 hours between connections.
While it has the deficiency in that its measures typically only cover a maximum of the most recent 60 or 61 flights - it would be better to have an annual snapshot -
FlightStats - Global Flight Tracker, Status Tracking and Airport Information has a handy 'flight reliability and punctuality' rating out of five. The worst flights (where excessive late running is prevalent and some cancellations occur) may get as low as 0.1 out of 5.
OD152 from PER to KUL has yet to be 'rated' by FlightStats, perhaps because it has not been operating for sufficiently long.
You are correct in that OD does not feature here much, but part of that is probably that I and others may not observe or record many of its late flights; the other factor is that with it using smaller aircraft, the representation does not stand out overly well on FR24 so I or others may have an unconscious 'selection bias' towards the twin aisle planes and hence not take as much notice of the B738s and equivalent as you might like us to. Apologies!
You could also check the alleged safety record at
Airline Ratings