If they are dead *NO*... If they are alive it should be encouraged..
Roman Catholics don't differentiate between asking for prayers hear on Earth and from those who have passed into the next life.
And in doing so they impart the God only aspect of omnipresence to dead people. (albeit very good people).
Someone in heaven is alive, not dead. Do you believe that heaven is not yet populated with any human souls?
If people all over the world can send you an email that doesn't make you omnipresent, it just makes you reachable.
If you believe that heaven is organized in such a way that its human inhabitants are unable to see or be aware of anything that happens on Earth, then you are correct that intercessory prayer is futile; but I don't see how you can justify that belief. it does not follow from "omnipresence is an attribute of God alone", that the "presence" of a saint in heaven is so limited that no information from Earth can become known to the saint. You don't have to be aware of every place at every time in order to be aware of a single person in a particular place at a particular time.
Noting one more for whom the concept of "alive in Christ" means nothing.