the game and show are interconnected. The game, being an MMO, is going to continually get additional content and evolve with the show. I chuckle whenever I hear someone say they are going to trade this game in because they "beat the game already" when it is just getting started. Look at the map. Look at all the unused space still available on it. And that is just in the Bay area. Give it a chance to evolve more. You only hit EGO 1000. I just hit 2000 and (current) max level is 5000. Lots more game to go.
As for your weapons. Keep the ones that max out that you like. Maxed out guns also gain an additional trait. Use them in areas where you can't level your guns anyway, like major arkfalls. Guns only level up when shooting things that earn you xp when you kill them ( and BMGs also level when you use them to heal a player)Also the xp bar on guns is the damage you have dealt with that gun. So anything you do to increase the damage (like overcharge) helps level it faster. And overkill counts, so if you do 2000 damage to a skiterling the bar will gain 2000 points of level. And leveling your gun in turn levels your skill.

Tomb Raider is very good, get it. Never played the multiplayer though so can't comment on that.