You need to define yourselves. This game has millions of players from all over the world. Each of those players has slightly different expectations, commitment levels, and focus areas.
You need to clearly define where you (as a guild) fit into this spectrum and then focus your attention on players who are like-minded.
Not having aligned (and reasonable) expectations up front is usually what causes these failures.
-Set minimum participation requirements and don’t accept players who can’t commit to them (ie: “600 daily and full participation in TB”)
-Set a guild goal and work together towards achievement it - then set a new, higher bar for yourselves (“We are currently at 43/45 in LSTB and working to achieve 45*!”)
-Look at the bigger alliances, they have their advantages and drawbacks but they can help to place aligned players in many cases.
-And finally - if you are looking at a merge, you need to be reasonable about that too. Almost every single failed guild merge discussion (that I have been involved in), has fallen apart for 1 reason: power struggle over the guild leader position. Everyone involved always thinks that their leadership is fantastic, even if they are falling apart and losing members left right and center. (“My brother Dave and I want to merge with your guild of 48 members, but you all have to join us because Dave is a really good leader”.)