You do not need Level 2 to use Time and Sales, since each tool stands alone, but pairing them gives a complete picture of pending intent and actual execution. The order book is all about pending interest. The tape records completed trades.
Level 2 displays "potential" orders, not actual executed orders. This is why time & sales is absolutely necessary when watching level 2.
Time and Sales is also more affordable and sufficient for tracking momentum or verifying whether large displayed orders are real or spoofed. Most active day traders will need level 2 + time & sales for precision entries and exits.