I don't think PvP has to be a big factor in getting HoM points - unless it's really good for making $$. Many of the items can be bought from players.. the mini's, weapons, etc. So I would finish the campaigns- save your gold to buy items from players. There are also players/guilds that run dungeons for gold. Completing the dungeons gives you the title credit.
I also heard that Nightfall and Factions give better xp and you level faster than Prophecies. I leveled to 10 in post-searing Prophecies - then jumped to Eye of the North and leveled to 20 very quickly.
Also remember they have said you can still work on HoM points after GW2 launches. Maybe some GW1 if GW2 ever goes down for maintenance (blasphemous!)
** and joining a guild that runs "speedbooks" and dungeons helps a lot. GoT or Guardian of the Turtle is pretty good.