Here are some suggestions IMO would improve the situation.
- Wins should award +50XP, Medals +10 and scale them up with the Tiers (+10 per tier)
- Any challenge that requires to do 3-5 “actions” (play 2 BTB matches, get one kill with a specific weapon, etc.) should be moved to the daily challenges, up to five overall; play a match + four other.
- Any challenge that requires more, than 5 “action” should be a Weekly, and make all weeklies available at the same time.
- Objective based challenges should be less specific. Instead of “Capture 10 flags”, there should be “Score X points for playing the objective”; like killing the carrier, returning it, scoring, etc. should count and add points to the progress.
- Mode specific matchmaking: Allow players to queue for specific game modes would remove the RNG from completing some challenges.