If I was to hazard a guess I'd say he was a Warrior, for if you re-read epilogue you find that he is planning to try out for the Heron Guard also heres my evidence to disqualify each type except the Warrior.
Strike one journal writer is not a Heron Guard.
I'd also say he's not an Archer, due to the fact that if he's planning on becoming a Heron Guard, as it is known from the flavor text of the Ghost Archers that Imperial Archers were only 2nd in greatness to the Heron Guard, it also relies on the fact the Heron Guard aren't archers.
Strike two the journal writer is not a Archer.
He can't be a dwarf as dwarves don't become Heron Guards.
Strike three the journal writer is not a Dwarf.
I wouldn't say he was a berserk as he voice does not fit with a Berserker, also I don't think berserks have ever became Heron Guards, also he was born in Strand, and Berserks come from the high North around the Twelves Duns and Gower and as it is clear from the Myth map, Strand is in the South not the North.
Strike four the journal writer is not a Berserker.
That leaves only one real possiblity, he must be a Warrior, even though there is not a Warrior on ever level does not mean he isn't one, as in Myth we only ever control a very small part of the Legion, menaing he could be on the sidelines or could hear the story of the battle afterwards, but then he never details the battles as if he was there, he just fills the stuff that happens inbetween each level.
The M2 Journal Writter concluding to logic is then a Warrior.
