purchase a regular account. Have that account invite 3 others using the RAF program. Group your 4 new accounts with your 70 paladin and clear instances. The 4 RAF accounts will enjoy the x3 EXP bump. If you invite 4 account using the 70 paladin account you will not receive the EXP bump while grouped. If you go that route start a new character on the pally account and level all up from 1st.

*Repeat of previous poster *