Doesn't Tosen lose to a normal captain? Well, the lieutenant was helping as well, but considering Ichigo took out three lieutenants with his bare hands, pre-bankai release, that shouldn't have been a factor. Point is, Tosen didn't get that big of a power up from going hollow.
Speaking of hollows, sure they may have done a high estimate of the power required to slice open a hollow moon, but that feat is still orders of magnitude higher then anything shown by Ichigo. I think the closest feat in comparison is Kempachi destroying a meteor. It's like saying blowing up a continent isn't that impressive because the continent was Australia. It may be the smallest one, but it's still a continent.