My bard design would be:
Mail Class, using instruments, 2 specs like DH, Int as primary stat
1. Healing spec: Using Harmony as resource - build up harmony with different elements (either melodies for casts or accords for instants), and release harmony with finishers (however you might call them) - singing and playing a melodic instrument like harp or a lute. Base elements have some kind of healing effect on the target (or group) - either normal heal or HoT - and have either a cast time or a CD.
All finishers would have some kind of a special positive effect on your group - depending on the finisher. Duration of the effect would depend on how much harmony you blow on it (similar to rogue combo points)
Examples (all AoE either on your party or on all targets in the range of your target): simple healing, HoT effect, damage reduction effect, haste buff, crit buff etc.
2. ranged DPS spec: Using Discord as resource - similar mechanic as with harmony - shouting and possibly percussion instruments. Discord spells deal either normal damage or DoTs and have either cast time or are instants with CDs.
All finishers would have some debuff effects on enemies in range of your target, depending on the finisher. Again, duration would depend on the amount of discord used (again similar to rogue).
Examples: increased damage taken, DoT effect, disorient / stun, silence, root, fear etc.
If you want to reduce the amount of weapons / instruments needed for one class, then I would fall back to the bagpipe as an allrounder, which was used by the Scots, a very combat-oriented culture.
Background: Armies always have musicians to accompany them. Why not have some bards / skalds then?
(Yes I know, the ministrel in LotRO works somehow similar to this concept. Was my favorite class in that game, and there kinda are no ministrel characters in the book, so....)