I decided to pull up where I leveled my bard 32-46. The following is a count of "you gain (party )experience" messages by zone and level.
Code:
level 32
total grouped solo zone name
152 109 43 all zones
137 108 29 Solusek's Eye
15 1 14 Lost Temple of Cazic-Thule
level 33
total grouped solo zone name
119 88 31 all zones
107 88 19 Infected Paw
10 0 10 Southern Plains of Karana
2 0 2 Solusek's Eye
level 34
total grouped solo zone name
190 148 42 all zones
134 93 41 Frontier Mountains
55 55 0 Trakanon's Teeth
1 0 1 Rathe Mountains
level 35
total grouped solo zone name
286 252 34 all zones
70 70 0 Infected Paw
60 60 0 Lost Temple of Cazic-Thule
43 43 0 Ruins of Old Guk
41 41 0 Frontier Mountains
27 0 27 Rathe Mountains
19 19 0 Southern Plains of Karana
15 15 0 The Feerrott
6 0 6 Grobb
4 4 0 Guk
1 0 1 Oasis of Marr
level 36
total grouped solo zone name
253 175 78 all zones
75 75 0 Grobb
70 70 0 Ruins of Old Guk
50 0 50 Lost Temple of Cazic-Thule
42 23 19 Iceclad Ocean
9 0 9 Oasis of Marr
4 4 0 Southern Plains of Karana
2 2 0 Guk
1 1 0 The Wakening Lands
level 37
total grouped solo zone name
181 83 98 all zones
91 1 90 Iceclad Ocean
90 82 8 Tower of Frozen Shadow
level 38
total grouped solo zone name
153 18 135 all zones
99 8 91 Iceclad Ocean
40 0 40 Crystal Caverns
14 10 4 Tower of Frozen Shadow
level 39
total grouped solo zone name
235 104 131 all zones
136 104 32 Tower of Frozen Shadow
57 0 57 Iceclad Ocean
42 0 42 Crystal Caverns
level 40
total grouped solo zone name
316 114 202 all zones
203 1 202 Crystal Caverns
113 113 0 Tower of Frozen Shadow
level 41
total grouped solo zone name
120 0 120 all zones
76 0 76 Butcherblock Mountains
33 0 33 Great Divide
10 0 10 Crystal Caverns
1 0 1 Eastern Wastelands
level 42
total grouped solo zone name
166 0 166 all zones
136 0 136 Nagafen's Lair
15 0 15 Castle Mistmoore
9 0 9 Kedge Keep
4 0 4 Kithicor Woods
2 0 2 Solusek's Eye
level 43
total grouped solo zone name
157 19 138 all zones
157 19 138 Nagafen's Lair
level 44
total grouped solo zone name
180 0 180 all zones
128 0 128 Temple of Droga
20 0 20 Oggok
12 0 12 Ruins of Old Guk
7 0 7 Nagafen's Lair
4 0 4 Grobb
3 0 3 Guk
3 0 3 Dreadlands
3 0 3 Mines of Nurga
level 45
total grouped solo zone name
214 0 214 all zones
180 0 180 Temple of Droga
19 0 19 Kithicor Woods
8 0 8 Ruins of Old Guk
5 0 5 Nagafen's Lair
1 0 1 West Commonlands
1 0 1 Guk
level 46
total grouped solo zone name
165 0 165 all zones
127 0 127 Temple of Droga
23 0 23 Nagafen's Lair
5 0 5 Kithicor Woods
5 0 5 Grobb
3 0 3 Lost Temple of Cazic-Thule
1 0 1 Southern Desert of Ro
1 0 1 Rathe Mountains
Going from memory on some of the notable camps, been a while apologies if I have misremembered:
The sola group at 32 was a bar camp duo with a shaman, a lot of fun. IIRC my sola soloing was starting at the zone line marked D and clearing towards #18 on the wiki map, but that might have been at level 30 instead of 32.
Paw was a pretty big grouping zone earlier. Doubt there's many groups there anymore but there's some opportunity to solo. IIRC basically nothing sees invis. The entrance mobs are lower level than later mobs.
Frontier Mountains at 34 was at the giant fort. Fun both grouping and solo, pulling in giants and charming.
CT used to be popular grouping too. I assume those solo kills in 36 were gator alley charm killing.
37 in iceclad: the dervishes around TOFS is one of the easiest bard pbaoe camps available. Already slowing by 38 -- if you change your mind and decide to skip 32-38 instead of exploring this is the place to go.
Feel free to ask about a specific zone and I'll try to remember it; maybe this list will give some ideas of places to try.