"We expected them to be a little bit stronger," Bierhoff told Goal.com.
"We were very focused. We have talented players with a lot of technique and other skills but the Irish team was a little bit disappointing.
"We know that they were missing some players but I think especially after going 2-0 up, we came back immediately in the second half with the third goal and the game was over."
However, Bierhoff was quick to add that Germany had better quality than their Irish counterparts.
"Playing against us, with our players is not so easy," he said. "I don't know about the whole situation here in Ireland. I know that Trapattoni is a big coach and has a lot of experience.
"He will know why he chose this way but we have these very fast, intelligent players - [Mesut] Ozil, [Marco] Reus, who is very fast, [Thomas] Muller is always creating something so it's not easy to play us."
Germany are currently at the top of Group A with nine points from three matches.