Wrath bow still gets FLB'd, yea. That's in the context of 'it won't be pushed out by other fire event SSRs for a long time'.

When is the interesting question, naturally. We are bound by ori and stars after all. Definitely look ahead to get a rough idea of what gets FLB when and do some casual planning.
Advent-wise, you want to set aside 2 (or 4) ori in ~end of December (Rahab), ~mid to late February (Typhon), ~mid April (Vritra), ~end of May/beginning of June (Mastema), ~end of July (Garuda), and ~mid to late October (Yatagarasu).
Union event, you want to set aside 3 ori/25 stars for each weapon for ~mid January (Envy) and ~end of January/beginning of February (Lust).

For the other elements? There are two ways to sort out priority. One is sorting by which 2nd skill you want. The other is by sorting by how much help do the other elements need.