As a player who has until the last couple of months or so only played Darkrai/Yveltal and have now been playing VirGen for the last couple of months, I am pretty confident in my match-up against Yveltal without Raichu.
I have been testing Abomasnow since Flashfire was released and feel very happy with it.
I had to look at it like this:
Do I include Raichu and strengthen 1, maybe 2 match-ups and still basically auto-lose to Pyroar/Fire? Or do I answer Pyroar/Fire and still have a solid match-up against pretty much the board?
Let's not make any mistake, Fire and Pyroar are basically an auto-loss. If your opponent is competent and plays well, there is very little you can do to stop the loss.
Abomasnow fixes that issue.
It OHKO's Pyroar, makes advantageous use of Virizion, is not immediately OHKO by Pyroar (without assistance anyway) and trades favorably against Charizard EX in the Prize race.
Whist Raichu does share at least 2 of the advantages Abomasnow has (Emerald Slash can set it up in one turn and it trades favourably against EXs), not having it does not mean you will basically auto-lose to any one match up.
It has been my experience that the Darkrai/Yveltal match-up is not as bad as people keep saying it is for VirGen. I have found that if you play well, use VirGen's natural strengths and abilities, and yes, have some half-way decent luck, then the match-up is probably more favourable than people seem to think it is.
EDIT: @Elbow
and if fire is the best then maybe we should add a colorless EX to the deck. How about tornadus EX? All we need is an EX that can do 90 damage and we can OHKO all pyroar.
I'm also now agreeing that raichu may not be a good decision.
You're not forgetting that EXs are basics right? And that Pyroar does not take damage from Basics??