Basically you can't. MNK is pretty crippled solo compared to how strong it is with a tank. It's not really a problem or anything, just means that soloing with MNK is slower than other DPS jobs. It's most annoying with beast tribe quests, but again, not actually problematic. You can stun and get a shot or two from the appropriate direction from time to time as well as when mobs ready a telegraphed attack, otherwise you just do lower than normal damage. Just don't try running around to get the direction bonuses. It won't work and will make you skip auto attacks (further lowering your damage output).