The issue with hackers has always been there, but ever since the 10th anniversary of gw2 the matches have been flooded with skids or bots that use a lot of exploits and cause the server to crash, if the server somehow survives the exploits it becomes "poisoned" and sets your max hp as 1, turns everyone invisible, makes everyone explode on death and have infinite bullets.
It is not safe to play multiplayer because the skids and bots are still actively targeting random people and getting people banned or ruining their accounts by making characters lvl up system completely unusable (meaning you won't get any upgrades to that character) and hacking your "gifts" section of the store making you unable to access the store to get more characters/cosmetics/abilities.