Grimoire does not equal skill. I have a Grimoire score of 4300+. Why? Because I hunted down each and every dead ghost in the game, found 48 of 50 Calcified fragments, have played since Day 1 and have tried PvP to a small degree. Your raid runs went well because everyone on your fireteam knew what they were doing, not because they had a 4600+ Grimoire score.