Since you seem to be equating serving in the Reserves or National Guard as dodging the draft, especially during the Vietnam era, how do you reconcile the following, using this Roll Call magazine article as a reference:

House Minority Leader Richard Gephardt - Served his country in uniform, 1965-71 in the Air National Guard. By your standards, Gephardt must've been a draft dodger, too. Don't be a hypocrit.

Other Democrats from the House who served in the Guard or Reserve during the Vietnam era:

Martin Frost (D-Texas) - Army Reserve
Charlie Gonzales (D-Texas) - Texas Air National Guard
Virgil Goode (D-VA), Va. National Guard
Joseph Hoeffel (D-Pa), Army Reserve
Jerry Kleczka (D-WI) Air National Guard
Edward Markey (D-Mass) Army Reserve
Alan Mollohan (D-W. Va) Army Reserve
Collin Peterson (D-Minn) National Guard
Robert Scott (D-Va) National Guard
Gene Taylor (D-Miss) Coast Guard Reserve

And from the Senate:

Jeff Bingaman (D-NM) Army Reserve
Christopher Dodd (D-CN) Army Reserve

As for former Vice President Al Gore, he served in the Army as a reporter for "Stars and Stripes", a cush assignment in the rear area where he could be protected from harm. You'd think a Harvard grad would qualify for more than being a Private using a typewriter.

There were Republicans who took the same advantages of the draft laws as Democrats. There were also Republicans who had distinguished military records. These include:

Randy Cunningham (R-CA) - one of only two fighter aces from the Vietnam war, nominated for the Medal of Honor, awarded the Navy Cross and many other medals.
http://www.house.gov/cunningham/about_duke.htm

Rodney Frelinghuysen (R-NJ) - combat engineer in Vietnam (Mekong Delta).

Jim Gibbons (R-Nev) - combat pilot in Vietnam and the Gulf War.

Wayne Gilcrest (R-MD) Marine Sgt. in Vietnam.

Duncan Hunter (R-CA) served as a Ranger in Vietnam.

Chuck Hagel (R-Neb) twice wounded in Vietnam.

Ted Stevens (R-AK) was a pilot in the CBI theater in WWII.

Strom Thurman (R-SC) served with the 82nd Airborne in WWII, receiving 5 Battle Stars (including Normandy).
http://www.senate.gov/~thurmond/pages/bio.htm

Back to the draft, it is a complex subject. The laws that affected the draft changed considerably over the years. According to the Selective Service fact sheet, there was a continuous draft in place from 1948 through 1973. The Vietnam draft era is typcially considered to run from about 1964 through 1973. Those of primary draft age were 18 1/2 to 25.

The eligibility for the draft depended on the person being able to meet the physical requirements. Certain medical conditions are disqualifiers for military service, including diabetis, epilepsy, mental illness, and sketal problems. Based on a physical exam and other criteria, each potential draftee was assigned a classification ranging from 1A (ready for service) through 1H (still in high school) all the way to 4F (medically unfit for service). Fathers were normally exempted from being drafted as well during the Vietnam era. Congress had authorized other deferment categories, such as sole surviving son, conscientious objector, and college students. The college deferrment wasn't an absolute. There were people drafted from college.

As for Dennis Hastert, he was born on Jan 2, 1942. He turned 18 in 1960 before the Vietnam war heated up. He turned 25 in 1967, the same year he graduated from college with a Master's degree. If he legally qualified for a college deferrment and didn't receive any preference or use any chicanery to avoid being drafted, I don't see a problem.

Dick Armey was born July 7, 1940. He turned 18 in 1958 when the draft was in low gear. By his 25th birthday in 1963, the Vietnam war hadn't heated up yet.