It's a bit strange to cater 2 rolls to one strategy which will end in less than a minute when doing so will take you 2 minutes to apply rolls, and 2 minutes to fix them afterwards. Although I have done stranger things in my career as a COR, it's usually because I'm not thinking straight about it. Yes, my general tendancy would be to use DRK+WAR roll for someone specifically using meikyo shisui, especially if the group is larger than just 1 person. With more than 1 SAM, unless they coordinate a very specific SC to use and stagger their meikyos to do it, they're just going to be stepping on each others toes.
The one situation I actually find allies roll to be useful is during a brew. Please don't get me wrong, I don't think any roll completely useless. There is always some bizarre situation you might find yourself in where any roll could be useful. But the original post is regarding which rolls this guy can get away with not buying in order to be a budget corsair. Obviously he's hurting his job by skipping any of them since someday even PLD roll might be exactly what's needed, but he values the gil more than the versatility. So my objective in these posts has been explaining which rolls will be less useful over a corsair's lifetime and why they're less useful so everyone could decide for themselves whether or not they agree.
Granted, the OP already got the answer he came here for, and now it's mostly just becoming a debate over which rolls are acceptable to skip over. In my honest opinion, the answer is "none", but I can understand the need to cut corners for a player without the means to make gil that I have. After all, corsair is fantastic at spending money, but terrible at making it.