You generally need to invest stats according to gear,yes.As to which stats are most useful,the most useful in most minion-heavy builds is Will,for a large power pool.Then if you're using ZF and/or pieces with many +stats,you'll need Stamina for more hp. (Drain Life's effectiveness depends on your hp pool size too,if you plan on that)
Accuracy is needed only when you're planning on using crit setups,and Strength is the least useful stat in most cases.It supposedly increases ZF/Sacrifice damage,but it's far too low a bonus to prefer it over more power/hp (or cdb if you're going for that).