With that out of the way, yes, I think 'directness' is of use in defining altruistic behaviour. If the action directly affects those others who benefit from it *and* want it, with little or no direct gain for the self beyond the internal happyness mechanics associated with such an action, then I think altruism is a pretty good term for it.
but is it useful to speak in terms of altruism, say, to suggest it is altruistic to rescue a child from an ignorant or abusive parent? The parent who wants a punching bag or wants the kid but just isn't good as looking after it will be affected, but I guess you'd say it was only indirectly, because it was directly for the child... but the parent indeed needs to be deprived directly, that isn't just a mishap that was avoidable, it was the expectation of your behavior being successful in liberating a child to a better life, so in a sense it really needs to be considered direct because it is in fact the means through which the good end could not be achieved without.
Do all direct effects need to be positive for an act to be regarded as altruistic? or alternatively, if an act such as exampled can't thus be considered altruistic (since to go out of your way to help someone else you must hurt a third person in the process), does it really matter that it isn't altruistic? is it somehow inferior to donating a dollar to a hobo, since that has no direct negative effect which the lifechanging salvation of the child does?
If something 'less altruistic' seems to be of more importance, what is the real value in the term? If we do acknowledge child services as a greater positive contribution than a dollar to a drunkard, then do we need a new word superior to 'altruist' to esteem them by since altruist, in such definition is inapplicable? We wouldn't want to say 'you're a good person, but you're no altruist' as if somehow they who devote their lives to hurting abusive people to help innocent victims don't measure up to the man who effortlessly throws spare change in a busker's guitar case doing nothing but directly positive acts.
If we can categorize people by their actions and label them a hero, a villian, a gentleman, a concerned citizen, and so on, without giving moral esteem, status, hierarchy to the groups, what good is being or not being one or the other thing? There must be an implicit 'better to be an altruist than a selfish man' concept, but do we not imagine, with altruism so defined that there is something more noble/respectable/etc than being an altruist? what are we to call that if altruism is reserved for even the most petty beneficial acts? It seems we'd need to radically rethink our perception of altruism as some sort of relevant category, and perhaps praise 'heroes' instead, altruism becoming a rather unimportant concept, and those who will kill tyrants and murderers, though by no means altruistic, the pinnacle of social esteem.