It's my understanding that we preserved a very ancient version of the creed. That is why we say "We believe," as opposed to "I believe." Making it in the first person plural is the more ancient way of saying it. Regarding the procession of the Holy Spirit, I think it's not in there because the version we say predates the controversy.
We reject the filioque and believe as the EO's do regarding the Holy Spirit. You can see this in the prayer in reply 2 of this thread:http://www.orthodoxchristianity.net/forum/index.php/topic,13200.msg183101.html#msg183101O Light! Procession from the Father, source of goodness, Holy Spirit of God, the children of the Church praise Thee together with the angels. At the rising of the morning light, shine forth upon our souls Thine intelligible light.
It's a beautiful prayer written by St. Nerses Shnorhali.
You might also want to read the following:http://www.orthodoxchristianity.net/forum/index.php/topic,10855.0.htmlhttp://www.orthodoxchristianity.net/forum/index.php/topic,2008.0.html