I didn't say that it was a "standard loadout," just that I could envisage Marines using many more weapon load-outs than in the rather limited wargame rules. Noting, however, that I did question the facility of the laspistol. (Admittedly, las-weaponry seems perfectly fine for the advanced Eldar, but there we go...)
As to multilasers? I just remember them back on anti-grav defence platforms back in the Eldar WD127 days. I just allow for the potential that they could have been included with Marines because they're "Mareenz" and are "awesome." The fact that this is not backed up in the wargame is another matter entirely. The fact that I could believe it probably says much about the overall standard of the novels than in the craziness of one particular author.
As to Goto? If you were to shoot every BL author that made mistakes with the materials, then you would probably need to rehire a lot of authors. What is artistic license to one reader is a mistake to another, a minor mistake to others, a hack job to others yet. Perspective and all that.
(For full disclosure, I didn't particularly enjoy the Goto novels nor do I think that he did the Eldar any justice. Then again, I think that about a lot of the BL novels so take that how you will.)