How critical are driveshaft balance matchmarks to oil retention seals?

Our 01 Ford Crown Vic had a trans rebuild (accidentally induced failure) and the franchised shop ignored matchmarks painted on the driveshaft and also those recommended to mark on dissemby. After two fast 1000 m round trips, the tail shaft leaked badly and the seal was replaced (n/c), again no balance marks observed per mechanic. After the next long trip, only 1600 mile later total, the 2.73 rear end pinon seal leaked heavily to a 6" oil spot after the trip, topped off with 40+ oz. The pinion seal was replaced and synthetic oil specified, again no marks on the pinion to flange, etc observed. The very next trip it failed with noise and two bearings showed lube loss marking said to be prior damage. To date $700 on two rear end services! Will it fail again without a pro balancing the driveshaft to get it back like it was? Are the seal failures front and rear from an un-balance or just the random occurrence of two sudden seal failure and resulting oil loss? The odometer from trans rebuild 43K, tailshaft seal replaced at 48K, pinion seal around 50K rear end bearing failure 52K.