My suggestion:
Cleric 2 > Bokor 2 > Diev 1 > Pard 1 or Orac 1 > PD 2
Cleric 2
This solo build has Cleric 2 with heal 10, cure 10 (nice damage until high levels when INT) Safety Zone 5 (30 blocks with max attribute), Divine Might 3 and Fade 1 (emergency exit!) and Deprotected Zone 1 (+1 debuff).
Bokor 2
Basic Hex (+1 debuff) + Effigy build. Put 5 points in Samediveve for mobility. Now you can choose Mackangdal 5 (+1 second per lvl) or 2, putting one point in each zombie skill to protect you using this monsters!
Dievdirbys 1
Support and more debuffs to help PD. Zemyna reduces 12SP to you spam more Effigy, and increase recover SP time for enemies (+1 debuff). Laima decrease cooldown of your skills and increases of your enemy (+1 debut) Both Statues in lvl 5 have uptime > cooldown, what keeps them running all time.
Pardorner 1 (or)
Increase Magic Resistance is only good with some points in SPR (not few). The must of this class is Discerning Evil, in lvl 5 gives +10 seconds of debuffs. It means Plague Doctor 2 with DE has 100% uptime Incineration without any debuff help.
Oracle 1
Arcane Energy 5 is 30 min of +15% SP, sounds great! Counter Spell 5 gives you 30 seconds of magic invulnerability and finish all magic circles near your. Put 4 points in Prophecy to alternate with PD Bloodletting and 1 point in Forecast just for Increased Nullification (giving you 5% chance of cancel any enemy attack) and keep it running 100% of time (duration 30s and cooldown 30s!).
Plague Doctor 2
No need to explain here. Max Incineration and put the rest as you wish, following your game style (More bloodletting and Healing factor to keep you alive forever or heavy invest in spamming debuffs skills to maximize damage and CC).
A important tip of this build is use the Incineration + Pandemic combo to spread Hexing. Just keep Bokor 2 (effigy 15 has a very high SP cost) and nail all enemies in your screen, while you burn with incineration.
I think it is a very solid build, with a good number of debuffs to extend PD Incineration, good survival capacity with Heal 10 and 3 skill for avoid status ailments (Cure, Bloodletting and, in a choose of Oracle, Prophecy), and good DPS with Incineration, Cure and Effigy.
