Well, there are alternatives to dungeon grinding and roulettes, but the trouble is they would take a bit longer, depending on how hard you do it - the vanuvanu daily quests and Rank A and S Hunts reward Eso tomes so that is something you can do in addition to a dungeon or two. As well, the Clan Centurio Daily Hunt rewards Centurio Seals which can redeem rather cheaply for gear formerly purchased with Law tomes, but that is slightly lower in ilvl than the Eso gear and thus on it's own wouldn't be sufficient for the Antitower. But with a couple of pieces of Eso gear you should be able to clear the ilvl requirement for it.