Namaste Skull Ji,
Its a good question, and I think that any sincere aspiring or attained transcendentalists or sadhaka that aspires for the enlightened goal what ever that may be will be naturally engaged in works that benefit all beings. but the questions begs what is the ultimate benefit, both Buddhists and Hindus agree that liberation from samsara is the goal and is the highest attainment and gives the ultimate relief from the distress and sufferings that come in the realms of samsara, Mahayana seems to think that Hinayana is a lesser path and has no concern for all beings and they are not engaged in Altruistic activities, and elevates itself as the path of the Bodhisattva as being superior to the attainment of Buddha, its not always like this but this misconception can creep in.
[QUOTE]Too much focus on liberation and unity with the 'eternal, all pervading' atman will result in ignoring all other beings/QUOTE]
I feel its a tough one to really put in this way, because full focus on our svarupa or eternal identity brings in the sense of one-ness or not being a separate entity, the individual Jiva more or less works for his own selfish needs and is dictated within his selfishness within the modes of nature, goodness, passion and ignorance, so until one comes to the stage of wanted liberation or to be situated again it ones own true nature then there will always be a trace of selfishness.
The problem of selfishness does not lie within the teachings of any particular school , for me this will remain within the individual, as most the practices of and complete understanding of any of the main accepted schools will have compassion, altruism and the search for total liberation as main tenants.
As for weather anyone once the objective self has been purified and arrives back at his original nature comes back into the world so to speak and works till each jiva is also back to his original nature within Hinduism may not totally exists, because once one has arrived back in his original nature he see's that nothing is separate from itself, so the concept of samsara and liberation does not exists, so what then exactly needs to be done....? I think most the deeper teachings of Buddhism also agrees with this