Considering your goals, I think the options you've provided are extremely well suited. I think the thing that sticks out is you want the Shaman and Druid as your base of healing, buffing, debuffing, and utility. Unfortunately, I cast my vote for PAL/SHM/DRU/NEC before I noticed the "other" option.
My "other" 4 box group for you would be:
1) BRD - best pulling tools, DOTs, DDs, snare, utility, excellent AC.
Role: Puller and MT
Justification: You mentioned a desire to do bosses. A BRD will pull them for you singly - guaranteed. Paci/AoE mezz/High Sun/Fading are incredible tools that even an ENC cannot match. Pacify pulling is much easier than FD pulling. This is an important consideration for a single player controlling 4 characters. BRDs wear plate armor, thus their AC can be as high as a WAR/SK/PAL. They will not be as capable as the heavy tanks due to poorer innate mitigation and avoidance, but your BRD will have very good support and healing behind him, so this is a none issue. The fact that BRDs can match the AC of the heavy tanks means they are viable as a MT to meet your goals. Need I mention all the other tools they bring to the table? Your BRD will be able to concentrate on singing damage and debuffing songs once the mob is in camp because he'll already be buffed to his limit, thus further increasing DPS a bit (no need to sing slow or haste or buffing songs).
2) SHM - Heals, buffs, debuffs, DOTs, procs, pet.
Role: Main healer, main buffer, slower
Justification: Is this necessary?
We bring it all.
3) DRU - Heals, buffs, DOTs, DDs, snare, long root, evac and ports, mana regen.
Role: Secondary healer, buffer, and debuffer, DPS and snare.
Justification: To meet your goals, the DRU is a much better compliment to the SHM than a CLR. Sure, you will lose some healing and HP buffing, but the literal ton-load of important abilities the DRU brings more than offsets this. The mana regen component of PoTC line alone is worth a CLR. The DRU is a better healer than the SHM, but using the DRU's mana to increase DPS through DOTing and DDs is a better use of his mana than using the DRU as primary healer. If I were running this group, I'd assign regen to the DRU and direct heals and HOTs to the SHM.
4)
In order of preference
a) ENC - Haste, Rune, mana regen, debuffing, CC, DDs, and procs (Boon of Garou, Tricksters, NDT, Mana Flare line)
Role: Buffing support, debuffing support, CC, mana regen, tertiary DPS
Justification: The primary justification for an ENC in your group is support. An ENC will take considerable load off your SHM and DRU, by taking up the hasting function, splitting the debuffing (ENC tashes and cripples, SHM malos and slows), and lightening the healing load with Rune (1500 points at 65). The groups DPS will also be increased through mana regen. The SHM and DRU will not have to be as conservative and can convert more mana to damage. The combat procs the ENC can cast on the BRD and pets can seriously boost DPS. (Permanent illusion AAs makes these some of the most mana efficient damage spells in the game.) The Mana Flare line can boost everyone's DPS as it procs from spells rather than melee (Consider that a BRD casts a spell every tick while using /melody and he can potentially proc it every tick.) With an investment of 9 AAs the ENC brings a fully commandable pet and he can use DC in Luclin/PoP content. While DDs are sad, they are efficient and add considerable DPS. He also brings aggro control and Fear for fear-kiting with the DRU's snare. True CC - your BRD is gonna be tanking so CC without the ENC will be through Druid root and Shaman VP. The ENC can mezz/memblur and get back to nuking.
b) NEC - Debuffing, DOTs, limited healing, mana regen, FD, pet.
Role: DPS, debuffing, limited group support
Justification: Trade the ENC for less support but add more DPS. The big advantage to the NEC is that he can debuff Poison and Disease resists to make both his and the SHMs DOTs land without being resisted as often. His DOTs are very powerful and his pet will add considerable DPS to the group. If the NEC gets a focus, the pet could even serve as as an off tank. Fear-kiting is enabled. Recourse DDs and DOTs add to survivability. Rez enabled.
c) MAG - maloxxx, powerful DDs, powerful pet, toys, CotH
Role: +++DPS
Justification: Poor group support and kind of a one-trick pony, but for pure 'bot-able DPS, they cannot be beaten. Massive mana-free DPS through a pet that can be the MT if focused, and massive nukes. They justify consideration on these strengths alone, but the ability to maloxxx, cast DSs, and CotH, and pet kits are nice additions.
Sorry for the lengthy justification of ENC, but I knew I'd get flamed if I didn't spell out all they bring to the table. Sure, its a weak class compared to others, but not as weak as many believe. Hell, the massive Runes and Mana Flare lines alone are worth putting up with their lame nukes. I hope this helps you.
Regards.