Like i said, stealth and guile are not something so crucial in the blademaster lore and concept, if you read their lore is all about being what i said, they are legendary warriors, they leaders and generals, by example among Maghterion army the blademasters were the leaders, they were not sneaky rogues, they didn't face illidan and the rest with tricks and stealth, they faced then head on in a fight. Ajd if you played RTS you know mirror image is not even leveled in most fighs, showing little importance comapred to just critical strike and the movement boost from wind walk, and that is their key factor, mobility, not stealth
they literally still said "Though blademasters are masters of stealth and guile,
they value personal honor above all else., no trickss, no sneaky rogues(guile means cunning, astuteness, warrior traits, not "deceptive tricksters)
Keep in mind that this is the
only part when they said they are "master of stealth", is from the WC3 game manual, (which literally go against the wind walk description saiying you are too fast to the naked eye btw, that is no stealth) and nowhere else, which implies is just the mechanic for that game, since nothing about that is brought up, expanded, explained later, not in wow not in the expansion who show the burning blade clan, not in the books, nothing
And they literally can add those two skills to the warrior class, without a single problem.