Well, I've played a few games using a 5 man meltacide scout squad and a rifleman dreadnought.
The Dreadnought has done reasonably well, it kills a few things every game so far. Its not been a game winner, as most of my opponents recently have been ap3 foot slogging armies.
I like the idea of a rifleman dreadnought, the theory behind them is solid. The 2 twin linked autocannons works well against light vehicles and a relatively cheap. The twin linked is also handy as it helps you to reroll missed hits (obviously). I have a tendency to miss about 2 shot a turn before rerolls, so they tend to help. However, my problem is I have only one riflemen dreadnought-which doesnt seem to have a great impact.
My meltacide squad has really impressed me. Its always managed to make its points back for me as well as being a really good distraction for my opponents. Its cheap so the squad doesnt break the bank either. My only problems are the fact that the squad is fragile because its so small and only has a 4+ save. Also, having to rely on them turning up when and where I want is tricky. Again, I think 2 squads of these guys would be more effective-rolling for 2 squads to turn up means that at least 1 of them is more likely to turn up when you want it (in theory).
I'm thinking of swapping out the dreadnought for another meltacide squad for my next couple of games. The reason for this is simply because the scouts are easier to convert. Also, it gives me the option of fiddling around with my army list to put some wolf guard into the squads to give them a helping hand.
Well, I'll let you know how they turn out when I get around to playing.
