The real annoyance you'll be facing if you want to go all the way to Tier Level 1, is the sheer amount of time grinding tier points to get there. That said, the Bad News assault rifle awarded for tier 5 is definitely worth it, and close enough to tier 1 to say wtf, might as well.
The big shame of grinding to Tier level 1 though is the only way you can actually play on that level is via mission replay.