More often than not, if two or more party members are afflicted with conditions, they are suffering from the same conditions. This may be due to area effects such as traps, or condition spreading spells such as Epidemic (or disease, which spreads itself). Conditions don't stack: drawing the same condition from separate allies does not add the durations, but rather the maximum duration is picked as the duration on the caster. To illustrate, drawing a 20 second bleeding from one ally and a 15 second bleeding from another would cause the caster to suffer only 20 seconds of bleeding, not 35. For the party taken as a whole, this therefore greatly reduces the total effect of all the conditions.
After drawing the conditions from allies, the caster can purge them wholesale with Purge Conditions or piece by piece with Mend Ailment. Mend Ailment is preferable if the caster is suffering from Fragility, as the healing effect will neutralize the Fragility damage. Needless to say, drawing conditions to yourself and purging is much more efficient than purging (many copies of) the conditions from the allies. Suppose three allies are suffering from three conditions each, say as a result of Virulence. Casting Draw Conditions three times and Purge Conditions once costs 20 energy in total. Mending the conditions from each ally would require nine casts of Mend Ailment, for a total cost of 45 energy.