What you have is neither grammar nor logic. If he who believes shall be saved then he who believes and is baptized shall be saved as well, yet it's the lack of belief that causes condemnation, and not the lack of baptism. If water baptism was absolutely necessary for salvation then, God would not make so many statements and which He promises eternal life to those who simply BELIEVE. (John 1:12; 3:15,16,18; 5:24; 6:29,40,47; 11:25,26; Acts 10:43; 13:38-39; 15:7-9; 16:31; Romans 1:16; 3:20-26; 4:5-6; 10:4; 1 Corinthians 1:21; 1 John 5:13 etc..). Faith alone still stands..
Asked and answered: Mark16:16 clearly sets salvation as dependent on belief plus baptism, not faith-alone, which the logic of the verse itself negates.