I took a stroll through the more recent teams that I can think of for awfulness:
2002 Tampa Bay, 55-106
2002 Detroit Tigers, 55-106
2003 Detroit Tigers, 43-119
1988 Atlanta Braves, 54-106
1985 Pittsburgh Pirates, 57-104
2010 Pittsburgh Pirates, 57-105
2002 Tampa Bay, 55-106
Bad. Very bad. They actually had a couple of guys who could hit - Aubrey Huff had 23 home runs, hit .313/.364/.520; Ben Grieve had 19 homers, Randy Winn hit .298/.360/.461 and Carl Crawford had just showed up for 63 games.
Apart from the mediocrity that the rest of the lineup sported (Toby Hall, Steve Cox, Jared Sandberg), the real problem was on the mound. Four starters, with ERAs of 5.18, 4.53, 4.83 and three guys who went 5.60/5.53/5.28 with the rest of the starts. The pen was even worse - the lowest ERA went to the closer, Esteban Yan, with 4.30 and the others were at least a run higher.
2002 Detroit Tigers, 55-106
2003 Detroit Tigers, 43-119
Chris Truby had 292 AB as the third baseman. Randall Simon led the team with 19 home runs and a .301 average; #2 in average was Bobby Higginson at .282. Carlos Pena's SLG of .462 in 75 games led the team, followed by Simon at .459. After that almost everyone else was in the .300s.
Jeff Weaver got 17 starts and had a 3.18 ERA. Beyond that, it was a horror show of 4.21, 5.52, 4.48, 7.77 (Jose Lima!) and four other fill-ins, all between 4.84 and 6.21. Juan Acevedo was the closer and a pretty good one, 2.65 ERA and 28 saves, but the starters and weak offense doomed this team.
In 2003 it was more of the same, except Dmitri Young had a very nice year as a DH - 29 HR, .297 BA, .537 SLG. Alex Sanchez emerged as a base stealer who got caught a lot and couldn't get on base. The team BA was even more woeful than it had been in 2002, and three regulars had OBPs under .293.
The pitching was even worse, as the relievers joined the starters in sucking hard. Nate Cornejo had the best ERA as a starter, at 4.67, almost a full run better than Jeremy Bonderman's second best at 5.56. Team ERA was 5.30.
1988 Atlanta Braves, 54-106
This team had Ron Gant, Gerald Perry, Ken Oberkfell as a regular and the ghosts of Dale Murphy, Ken Griffey, Ted Simmons, Lonnie Smith, Bruce Benedict, Gary Roenicke, etc., all of whom got significant playing time to prove they had nothing left in the tank at all. Well, Murphy hit 24 home runs and 35 doubles, but his BA was .226 in 671 plate appearances.
The pitching staff wasn't horrific, it was very young. Rick Mahler was 34 and the #1, but the rest of the staff was 22-year-old Glavine, 22-year-old Pete Smith, 27-year-old Zane Smith, 23-year-old Kevin Coffman and 21-year-old John Smoltz. They all struggled, they all had WHIPs between 1.35 and 1.73.
1985 Pittsburgh Pirates, 57-104
This team had Johnny Ray, who led the starters in BA at .274. It also featured some last gasps by Bill Madlock, Steve Kemp, Jason Thompson, Lee Mazzili, Sixto Lezcano and George Hendrick, none of whom did a damn thing.
Rick Reuschel came out of nowhere to go 14-8 with a 2.27 ERA; after that it was Rick Rhoden, Jose DeLeon, Lee Tunnell and Larry McWilliams serving it up early and often. Candelaria was the nominal closer. Kent Tekulve ended his career with three games and a 16.20 ERA.
2010 Pittsburgh Pirates, 57-105
This team was bad but also very young. Garrett Jones was the established slugger with 21 HR and a .414 SLG. Lastings Milledge hit his high water mark with 113 games and a .277/.332/.380 slash. New kids on the block were Neil Walker, Pedro Alvarez, Jose Tabata and some guy named Andrew McCutchen.
On the mound they had Maholm, Zach Duke, Jeff Karstens, a 1-11 Ross ohlendorf, a 2-12 Charlie Morton, and the immortal Brian Burres. Dotel closed and got 21 saves in his time in purgatory.
Those are some awful teams. I don't think the 2012 Astros would be better than all of them, but those Tiger teams were truly, historically woeful. I think they're the bottom of the barrel for sure, followed by Tampa and the '85 Pirates. That's about where I see this Astro team coming in, fifth from the bottom. Ecch.
What this doesn't speak to really is trending upward from the bottom. Most of these teams rebounded pretty well and pretty quickly, and if that happened to these historically awful teams, it's a decent bet that the Astros will come back up for air too.