I've been involved in the 40k hobby going on 20 years, mainly from a modeling and painting point of interest, and I generally feel that I've got a good handle on what armies are supposed to be good at. The catch to that statement is that until about 3 months ago I almost never played. The 3 game stores that were within a half hours drive of me have all closed leaving my only options as 1 location that is 45 minutes away, 1 GW store that seems to be inundated with circuit Tournament players and is an hour away, and another GW store more then an hour away in the opposite direction. Mostly by chance I've gotten involved with a local gaming group recently and in the last month I've played more games then I had in the prior two years. So now I'm actually playing games. I find myself struggling with Orks. In one game the Ork players Deff Dread was bloody near un-killable has it survived 3 rounded of concentrated krak missile barrages, Conversion beamer attacks, and a single round of close combat with my Iron Clad (Which the Deff Dread absolutely ate). In another game I was simply unable to inflict enough wounds to affect the outcome of close combat when it hit me. 3 PK attacks aren't that scary. 3 PK attacks with 19 ablative wounds... okay now I've got a problem. And then in our most recent game she took a BattleWagon just for grins and giggles and no matter what I hit it with or where I hit it not once did I do anything more then stun the monster. I know these are all one-off examples of "The Dice gods just hate you", but I would like some feed back on my army and what I should be doing with it. Here is my current work in progress list for 1000 points:
3x Tactical Squads (10 men broken into 2 combat squads)
-Sergent W/ Powerfist
Razorback With T.linked Heavy Bolter and HK Missile
Predator with Dozer blade, Extra Armor, Autocannon, HK Missile, and Heavy Bolter Sponsons.
My general battle plan is to break my Tactical squads into Combat squads comprising 1 sergent, melta gun, and 3 bolter marines in the razor backs with the Missile Launcher and 4 Bolter marines providing cover from behind. The Captain goes in the lead Razorback and the Razor backs move forward, with support from the Predator, to either hit a selected unit hard or to claim objectives.
In my mind I have a pretty solid list and battle plan, but my mind rarely translates to reality, so I'm looking for a more objective look at it.
It certainly does sound like you hada bad run of dice there! It's important against the Battlewagon to bring shots tobear in its side AV12 - use your Razorback mobility for that. Otherwise when all else fails - meltagun to the face.
The list is okay but a few things. At 1000 points, 30 Tactical Marines is too much. Drop a squad. I'd also not be running a PFist on the Sarge - you don't want them in close combat and only four extra wounds means death. Instead give him some sort of combi-weapon. If you find you're struggling with hordes, a flamer; vehicles, a meltagun (sounds like this is your best option here). Also upgrading the Bolterback to a LasPlas could really help your anti-vehicle problem (reverting the combi back to a flamer).
I'd also look to change the Captain to a Libby - more utility though you won't see much of it at smaller point levels. That being said, with the points saved from the Tactical squad one of the options I would suggest is a Sternguard squad in a Rhino - outfit with some combis and maybe a PFist and the Captain has a perfect place to go here and if you drop the extra armor, hunter killer and dozer blade off the Predator, have enough points leftover for a 2nd Predator to give you more ranged dakka as well.
That's a pretty big shift in list but for essentially the loss of five Marines & a missile launcher you should double your ranged anti-infantry and get a lot more melta onto the table. Hopefully that helps out!