C# - Object Oriented N-tier Design Abstracting Too Much?

I'm building my first enterprise grade solution (at least I'm attempting to make it enterprise grade).I'm trying to follow best practice design patterns but am starting to worry that I might be going too far with abstraction.

I'm trying to build my asp.net webforms (in C#) app as an n-tier application.I've created a Data Access Layer using an XSD strongly-typed dataset that interfaces with a SQL server backend.I access the DAL through some Business Layer Objects that I've created on a 1:1 basis to the datatables in the dataset(eg, a UsersBLL class for the Users datatable in the dataset).I'm doing checks inside the BLL to make sure that data passed to DAL is following the business rules of the application.That's all well and good.Where I'm getting stuck though is the point at which I connect the BLL to the presentation layer.For example, my UsersBLL class deals mostly with whole datatables,as it's interfacing with the DAL.Should I now create a separate "User" (Singular) class that maps out the properties of a single user,rather than multiple users?This way I don't have to do any searching through datatables in the presentation layer,as I could use the properties created in the User class.Or would it be better to somehow try to handle this inside the UsersBLL?

below is the code from the UsersBLL:

using System;
using System.Data;
using PedChallenge.DAL.PedDataSetTableAdapters;

[code]...