Poking around with druid I really enjoyed jumping between wolf form, bear, form, and the 2 elemental forms. While doing this I noticed that many (but not all) the buffs specific to forms would vanish when I changed forms.

Some buffs like animal form would remain active (but suppressed) while I was not in animal form. When I turned back into animal form it would re-activate. This mechanism is one that I really enjoyed.

Other buffs like the elemental toughness (5 dr/-) would vanish when I left elemental form and would not be re-aplied when I turned back to elemental form.

My suggestion is this: If you want to encourage players to switch forms often in quests then change most of the form specific buffs to be merely suppressed instead of removed.

If you want to encourage players to specialize into forms and switch infrequently then keep things the way they are.