Access to Legendary Weapons in Blade and Soul
When you get to Level 45, everything becomes different. The good news is that you do not need to level up your main story weapon the entire way. More weapons open up as viable.
First, you get access to the Silverfrost weapon. This is currently not very good, but it is worth keeping around just in case. The developer does make changes to the weapon system that affect which weapons are good. After you make progress through Act 4, you will start to get access to the S - series of legendary weapons. These weapons provide a more diverse selection and are more suitable for the endgame content. The main story weapon is not terrible, and it is possible to keep using it and evolving it, but it is not the strongest weapon available once you cross over into the last few levels and hit the level cap.
The S - series system is still in flux, and right now they are mostly useful for PvE and the open PvP system. Arena PvP automatically equalizes gear for everyone involved. There is a battleground - style PvP in development that will involve larger groups fighting it out, and gear will not be equalized in that mode. However, it is still some time off, and it is very probable that there will be further refinements to the weapon system between now and when it arrives.
The best approach is to make use of your main story weapon, upgrading as you need it, until 45. There are even quests now that drop evolved forms of the main weapon as rewards, so you may not even need to upgrade it yourself. After you hit level 45, then you can start looking at the S - series and decide which of those weapons you want to pursue next. The grind starts to become significant, but the increase in power is also significant. Higher levels introduce the idea of failed upgrades. The breakthroughs or evolutions have a chance to not work, consuming the materials but giving you nothing. As you can imagine, this is frustrating and adds to the grind.