In addition to what MLinni said above, if you could get your hands on some gathering boosters, they help a ton in obtaining the vials each time. I think you can use the following boosts for this:
https://wiki.guildwars2.com/wiki/Gathering_Booster
https://wiki.guildwars2.com/wiki/Guild_Gathering_Boost
https://wiki.guildwars2.com/wiki/Guild_Gathering_Banner
As for Shatterer, since only about 5-6 people who are closer to him seem to get encased each time, it might be a better idea to try and join a “not so populated” map in order to increase your chance of getting encased. I know this isn’t as easy as it sounds, but showing up a bit late to the event (after the initial zerg maps are formed) could do the trick. Just make sure there’s enough people around to actually finish the pre-events and you’ll be fine
Good luck and have fun in your journey to Bifrost!