BENGALURU: India's top private lender HDFC Bank has warned that its merger with HDFC Ltd would hit key financial metrics including its margins and bad loan ratios, sending shares down 4% on Wednesday and dragging the blue-chip Nifty 50.HDFC Bank's gross bad loan ratio is expected to have increased to 1.4% as of July 1 post-merger, from a standalone 1.2% in the June quarter, while excess liquidity from the merger is seen dragging the lender's net interest margins down about 25 basis points.The bank provided the outlook at...