My highest team (SHD, CLE, BRD, ENC, WIZ, ROG) is only 72, so I'm not sure how this advice applies to higher levels. I also have another team at 50 (SHD, SHM, DRU, MAG, ENC, NEC), which I created to specifically test how I would fare without a cleric or bard, so I can at least make some observations.

A bard is an awesome addition to any team, for both run speed (although that becomes less important after you have Run Speed 5) and reliable group invis/lev. The latter (via Selo's Song of Travel at 51 especially) is incredibly useful. Your druid will get a group invis (Foliage Shield) at 52 and has single target levitation but there is not group version of improved invis that I am aware of and only necros get group levitation (that I am aware of). A bard can also do crowd control, but they need to concentrate on crowd control when they do so, meaning that you won't get all the benefits of /melody at that point. They do have awesome crowd control tools though.

Mana regen from bards and enchanters is comparable (when the bard is able to play that song). If you play in outdoor zones, having a mount makes a huge difference. Of course, once again you will run into the issue of what the bard should be playing using /melody. If you are doing heavy crowd control with the bard, you may not get all the mana regen benefits they bring. You also have the Pot9 line for mana regen on your druid, so you may find you have enough even with a bard who can't play the chorus/cantata line all the time.

One issue you will have in going without a cleric is the lack of resurrection until level 59 when both the druid and shaman get a 90% rez. The cleric gets steadily higher percentage rezzes, topping out at 96% at level 56. Clerics are amazing healers, and for most group content so far I can just use a Heal over Time, particularly once the mob is slowed. The issue I foresee with the druid/shaman combo is that they may both need to heal until the mob is slowed and that if you take out the enchanter, then the shaman is your slower. You could try the bard as a pre-slower (from level 48), at least until you have a pull under control and get a chance to overwrite with the shaman slow.

Overall, I'd say you'd have a slightly easier time with the group you have now, but the group you are proposing should be able to do the same content. I'd be interested to know what you eventually decide to do and how it works out.