Aside from China, no, according to a new IMF working paper by Marta Ruiz-Arranz and Milan Zavadjil. This is in large part an attempt to insure against a repeat of the 1997 Asian currency crisis:
The paper has presented evidence that to a large extent explains Asia’s large reserve accumulation since the 1997–98 crisis through the precautionary motive. Current reserve holdings in most of Asia (excluding China) are not seen excessive when compared with levels predicted by a simple model of optimal reserves applied to specific country and regional characteristics. By mitigating the potentially large welfare costs of crises, reserves provide benefits in terms of insurance that more than compensates economies for the
opportunity cost of holding liquid assets.
Large currency reserves have the added benefit of lowering borrowing costs:
Furthermore, the benefits of reserves in terms of reduced spreads on privately held external debt, and thus borrowing costs, further justifies most of the observed growth in reserves. The paper finds that a majority of economies in Asia continue to benefit from reduced spreads, as evidenced by the high estimated threshold levels beyond which no further gains are realized.
Nonethless, the authors consider that current reserves "are close to or have recently reached optimal
reserves levels", and "a slowdown in the pace of accumulation in Asia is now desirable."
China, meanwhile, remains an anomaly. These models "cannot fully explain the large stock of reserves in China" - a subject to be explored in future research.