Make that Keeper work and all fight close to each other !
This is exactly why Sarre is the be-all and end-all - global barrier from any locale. However, your point about staying to together is crucial if xp generation is your goal. And Keeper is a great xp generator if constructed and played properly.
My unsolicited tactics for maximizing xp.... When I played with Vlad, Elf, and JP, we'd use these tactics and often exceed the team xp cap (~130k). Thus promoting in two runs (15-20 minutes each).
1. Ensure every team member hits every enemy
2. Ensure every team member is hit by every enemy
3. Ensure there is a team-wide barrier at all times (Saare, Virt, Keep). Hits while a barrier is active increases xp. Kills with active barrier creates support xp
4. Run the castle, no dragon (yields 1-1.5 more level points)
5. Use one or more Lego...counter strike, war cry, shield wall, payback strike (greater hit radius than shield bash). 40-50k xp
6. Use one or more Saare...saar-taar, itwa, gaatlok, athlok (barrier, range, aoe, combos) 40-50k xp;
7. Virt and Keep are second to Saare. AW is third (no global barrier)
8. Any other warrior is a very distant second to Lego. However, Kat w/ Dancer's is good as is Avvar (wrath, charge, leap)
9. No reavers, no sisters, and certainly no damn assassins