Adding lead to a racket sometimes helps with arm problems, especially with the PD due to a high RA, low swing weight.
Poster still has not responded with what string and tension they are using which might be part of the problem. At the stock TW swing weight of 308 and a 72RA some players are going to have arm problems. To what degree depends on tension and strings. For some poly is going to be a arm killer. Still you can work with the racket, I have several customers playing natural gut/poly crosses at 50/46. I have others playing full gut at 45. There are many answers to this but more info from the poster is needed. I play with the PD 2012 rackets at 324 SW, full gut at 60/59lbs with no problems.
3 Matched Pure Drive 2012, SW 324, 2pts HL Nat Gut Can you say "Surgical Precision!" Eagnas 910 stringer. Wise tension head ERT 300