This is not necessarily true and depends on your build. BM has +50% chance to poison on melee hit only and +75% poison dmg for yourself and your minions.
If you run a build with just one companion Druid gets +75% to all personal damage, +40% chance to poison on hit with melee or spells for yourself and your minions. Druid also has an 80% damage over time node. Druid also gets automatic access to roots (although this is so low in the tree that BM can easily dip into Druid to get it) which can be specced for an 8 second buff to all damage which provides a 100% boost to both poison and damage over time.
The fact that Druid minions get poison on spell hit bonuses means that you can get more out of thorn totems. Get some combination like the 5 totems at a time, all the poison chance and duration nodes and be getting a whole lot of poison sources.
BM is I’d say an easier Serpent Strike build but Druid can definitely provide some poison benefits if you build for it.