Thanks everyone for the input. As per Gutstikk's request, I'll include what I can remember of the games that I played. I've only played this list against MEqs. I don't remember all of the opponents, but I know they were MEqs. Of the ones I remember:
A Deathwing list (lots of Terminators, whirlwind, scout bikes, dev squad with lascannons, Dreadnaught)
A Ravenwing like list (3 Speeders, a couple bike squads, Land Raider, Special Character on bike/speeder)
Assault heavy marine list (Librarian and Chaplin with assault upgrades, Assault squad, HQ squad with cc weapons, Terminator squad with 2 assault cannons, devastator squad)
I don't remember all the specifics, but in each game we had random missions and level. None of my games were escalation.
The first thing I will mention about this list is that terrain is very important. I always play with at least 25% coverage. It is essential to keep units hidden at various times.
The Dark Reapers and the Vibrocannons provide the long range shooting in this list. They are there for two reasons. First, they can cause quite a bit of damage to any squad that tries to sit back and just shoot at them. Secondly, they are area and game control. I don't usually expect any of these squads to earn their points back. They are there to suppress the opponent. I use them as area control to block certain avenues of approach and to bait the opponent into coming where I want them. If I do get good shooting, then they perform the second roll anyway. The vibrocannons tend to intimidate the opponent into placing their tanks in the very back or opposite board side. I will gladly us 100 points to stop a tank from being a threat because of where they placed it. The Dark Reapers perform the same function against infantry squads. I usually set them up in somewhat exposed places to make sure they have good shooting lanes and stop the opponent from setting up where infantry will likely get shot early and often. Once these are done, I will use Divination to move the squads into good firing lanes, noting the final setup.
My Dark Reapers and Vibrocannons also help out the assault units. Usually my opponents choose to send their assault units to deal with my fire base instead of trading shots with them. This helps the Scorpions and Harlequins get into assault earlier.
The Dire Avengers usually work as a single group, with the Defend squad in the front. They always advance towards terrain that blocks sight to them on the first one or two turns. After that, they will either advance on firing lines or do a fallback while shooting at advancing enemies. With these, I'm most worried about Dreadnaughts and Monstrous Creatures getting into combat with them.
The Warp Spiders will also work as a single group most of the time as well. The second squad is used to ensure that casualties are great for any infantry they are going after, or to add additional shots into tanks. This squad usually hunts light tanks first and then moves onto infantry. I don't use their assault jump much because I don't want them to get too far away from support.
The Scorpions and Harlequins will change rolls depending on what the enemy does. If the opponent has much assault, they will hold near the fire base to be counter charge units. I tend to always set up where I can get the charge. If the opponent stays back, then they advance together along a flank to start combat with a firing line. The two units usually provide enough cover and threat that they can deal with most any single squad. Most of my opponents never try to overwhelm them with 3 or 4 squads when I advance, so they survive for the most part.
Eldrad has a number of uses in this list. He will first use Divination to help me make the most of my firing base. When the game starts, terrain will determine the first powers he uses. If I can hide the Scorpions well enough, then he will Fortune the Reapers and probably guide them as well. Otherwise, the opponent usually gives clues as to whether he fears the Scorpions or Reapers more and then whatever he fears most will get fortuned. The first turn he usually doesn't join a squad. In subsequent turns, the opponents movements will dictate different powers, but I tend to always have at least one squad fortuned and one enemy doomed. My favorite use is to put him in with the Scorpions and go on the offensive.
The Jetbikes are the one squad I will let go by themselves. Mostly, this is because nobody seems to care about the small squad. I like to use them to go after tanks. Their speed and lack of apparent threat lets me get closer than I should before any attention is given. Against a horde list, they would probably stick close to the Warp Spiders and then flamer choice targets and then try to get away.
Now for how things went in my games.
The game against the Deathwing army was scary. I knew he would be deep striking his terminators into the battle and that the scout bikes would get them in choice locations. I tried to bunch most of my squads into a corner to prevent some of the damage. As it turns out, the terminators didn't do much that game. They shot at Fortuned Reapers in hard cover and then died to massed fire and Harlequin assaults. The Vibrocannon took out the vindicator after a few turns. The two problems I saw were the scout bikes and the Dreadnaught. After taking out the terminators my assault units were out of position and the bikes attacked my fire base. They took out the Vibros and a squad or Reapers before I could get back with Scorpions. The Dreadnaught was advancing as well and I had to send the Harlequins in to stop it. That combat lasted a number of turns and I lost several before I finally killed it. This was a point where I had the tools to do what I needed, but he pulled me out of position and got quite a few kills in.
The Ravenwing game didn't cause me any issues. The Warp Spiders and Vibrocannons took down the vehicles while the Dark Reapers took down the bike numbers. I used the Dire Avengers as a speed bump against his assault squads in order to get good position with my Harlequins and took out most of his force. I don't think this game could have gone much better for me, but a big part of it was that my opponent didn't respect the lethality of most of my units.
Against the assault based Marines, I also had a very easy time. The Dark Reapers pounded him on the way in and when he made it into assaults, my squads had no problems taking down the last guys. I didn't lose many models in this game and I think the biggest issue was that my opponent was too hasty and didn't use terrain to cover himself enough on the advance.
And now there are a few things that I would consider on this list. The first change I might make is to replace the smaller squad of Dark Reapers with another set of Vibrocannons. This will limit my MEq killing potential a little, but will make me better against vehicles. I'd also get a few more points to get Withdraw on the Warp Spiders. I might also consider using a squad or two of guardians instead of the Dire Avengers. This would give me a few more bodies and some more long range threat, but I'd lose the tar pit of the Dire Avengers and their higher range guns.
I would like to get some experience against none MEq armies, but that is usually what I play. I think this list could still do very well, but I don't know yet.
And now that I'm done, I hope it all makes sense.