This SRO guide is awesome; we are using it step by step. We lower the mobs attack power plus increase our phy/mag attack power, therefore the pt mobs die faster. We are just wondering we should get the buffs for str/int for the cleric or just bless spell. We also got the shield trash; it is so useful for the warlock. The STR/INT buffs are entirely optional.
However if you decide to get them you might as well go full party cleric and get most of the healing skills. If you have the SP to get the entire Cleric tree as well as your Warlock (Silkroad gold) tree, you can be wonderfully flexible in parties. Allowing the party to carry on after the main cleric logged off; just today we were both a party cleric and a warlock. Like you said, Warlocks are very good in parties and are often underestimated for their abilities. Scream Mask alone is enough to invite one.
We like to cast it on the wizards so that when they do AOE nukes, they stun a bunch of mobs at once. Another good target would be the healers so that when monsters attack them, the monster may be stunned. Allowing the healer time to escape. The debuffs are awesome for party monsters all around. We assume your cleric mastery is 10 below your warlock mastery since you have warrior mastery at level (Silkroad online gold) 10. In that case, do not get the buffs.