Because it's his problem with Gateways that made him late! He should be more effective at them based in his strength.

Logain's comments are just another example of characters thinking they know something they do not. The fact of the matter is Logain's rationale for thinking Rand is stronger than him is dead wrong. Yes his end assumption is correct, but that is besides the point. We don't have nearly enough evidence to assume that there are few people with Shielding Talent. He'll it could be incredibly common, Lanfear's shield on Asmodean was very impressive as it held him partially despite his Raw strength likely being greater than Lanfear's (effectively she is clearly more potent, but you seem to think Strength is the key to these things). Shemarin puts on an impressive Shielding display as well ... She manages to hold 3 relatively Strong AS at once... Unless she is much more powerful than is likely for an AS I don't see how that is possible without the Talent. There are probably other examples in the text as well.