List of Level 50+ people with low defense (Updated 3-14-13)

You can battle these folks to gain mastery faster by getting +3to5 each battle
The more levels they are higher than you, the more mastery is added per battle.

Deepblue4550 (lvl 90)
Hirkyflobble (lvl 78)
Primo911 (lvl68)
Monito5 (lvl67)
Cintax 33 (lvl 74)
Bigpapi11239899
Shanefearn (lvl 83)
Quachrtq (lvl 71)
Jumpymcspasm (lvl 106)
Lyn3tte (lvl 90)
Gibsupup1 (lvl 81)
skinner199 (lvl 73)
Joeblow79 (lvl 72)
Eiditrosen1 (lvl 68)
Monsternub (lvl 65)
Catholicrusader (lvl 62)
Annmarl (lvl 61)
LixefR (lvl 61)
zeratuld (lvl 60)
Plehboi (lvl 59)
minimuscle0 (lvl 58)
Rvgrand2 (lvl 58)
ikvantage (lvl 58)
Anthonyv6454 (lvl 57)
Pfua671 (lvl 57)
jfidnucks (lvl 56)
Aramyth51 (lvl 56)
Mabasesyndrome (lvl 50)
Predicus (lvl 74)
dannycoker814 (lvl 71)
deathsxwill (lvl 75)
hulkingapoc (lvl 62)
jackyjack00 (lvl 80)
SSTRONK (lvl 74)
schloffatm (lvl 74)
lemi28 (lvl 70)
nuggets33 (lvl 68)
y0Liis (lvl 83) (Uses 5 Mockingbirds, so use more than 1 card in your deck)
solvicious (lvl 67)
qlaplace (lvl 72)
Goma777 (lvl 90)
erictt55 (lvl 92)
fragment08 (lvl 76)
Jclen11 (lvl 69)
Jabronii (lvl 76)
trcoba3 (lvl 75)
trcoba4 (lvl 74)
Orenxpress (lvl 64)
Dunbar98 (lvl 76)
Athena2317 (lvl70)
TORCH3D (lvl 58)
mycool13 (lvl 71)
Orion777 (lvl 62)
EliWalshe (lvl 57)
nornor1515 (level 75)