The bracket shrinkage is affecting all the midbrackets, not just 29s. Yes, drama heavily affects any XP-off midbracket. People play XP-off strictly by choice now; it doesn't happen by accident (once you surpass the 20-24 bracket), and midbracket players by and large prefer to spend their limited PvP time in brackets that are more fun and less prone to personal attacks and asshat attitudes. 39s, which for over a year the most populous bracket of all the midbrackets, managed to troll itself out of existence. While getting players from other brackets may help in the short term, I'd argue that all the midbrackets will need to recruit fresh blood from outside of the midbrackets, and hopefully outside of twinking.
Every twinker bracket thread on the WoW forums would benefit from an intro paragraph that sells the no-XP philosophy to visitors. Something like....
"Do you love battlegrounds, but hate playing alongside farmers and bots? Do you love finally completing your gear, but hate to see it fall obsolete in months or even weeks? Does your guild schedule RBGs, only to get stuck hunting for filler players?
"You deserve a better PvP experience. Find out what thousands of PvP'ers already discovered: XP-off stops the bots, stops the gear treadmill, and stops the players more interested in leveling and farming than playing for real. If you have the diligence to gear up, the desire to win via team coordination, and the dedication to master team communication, then XP-off battlegrounds await your discovery.
"Stop your XP at 29, gear up, and queue for Warsong Gulch every Tuesday and Thursday at 9pm EST/6pm PST. Discover why game nights continue two years after Blizzard introduced no-XP battlegrounds. But be forewarned: 29s play for the love of PvP. The intensity, camaraderie, and fun may spoil your ability to ever go back to XP-on."
...Customize to taste for any schedule and bracket.
Everybody wants more players in their bracket. But nobody wants to deal with newbies. At some point, us XP-off players will need to get over our elitist PvP attitudes and resolve this paradox by taking a more proactive role in making a difference for the brackets we love. If we would run a player through an instance, maybe we can help a player practice kiting and interrupts. That's how we grow a midbracket. The most prominent features of 29s or any midbracket are not balance nor population. Instead, promote the higher quality PvP, camaraderie, and relative midbracket ease of gearing for 29s, and we will see progress.