See the bottom of the description for the most up-to-date tier list. Also, see these videos for the newer heroes added:
Dianyun:    • Dianyun Hero Review - Kingdom Rush Ve...  
Ten'Shí:    • Ten'shí: Thorough Hero Review and Ana...  
Grosh:    • Grosh Hero Review Kingdom Rush Vengeance  

TIMESTAMPS:

0:00 Introduction
9:25 Heroes' Epic Moments Montage
11:10 57
13:45 56
16:34 55
19:43 54
24:49 53
28:40 52
30:38 51
36:32 50
39:33 49
42:55 48
46:30 47
49:35 46
55:11 45
1:01:31 44
1:07:03 43
1:11:23 42
1:16:04 41
1:18:14 40
1:21:50 39
1:26:18 38
1:33:30 37
1:40:08 36
1:44:35 35
1:49:12 34
1:52:33 33
1:57:33 32
2:01:22 31
2:04:59 30
2:09:19 29
2:14:27 28
2:17:45 27
2:20:34 26
2:27:10 25
2:30:13 24
2:32:53 23
2:37:58 22
2:42:06 21
2:46:50 20
2:51:50 19
2:54:25 18
2:57:52 17
3:02:46 16
3:07:43 15
3:10:59 14
3:15:45 13
3:21:50 12
3:25:58 11
3:32:51 10
3:38:00 9
3:41:35 8
3:49:47 7
3:53:15 6
3:58:33 5
4:06:30 4
4:13:51 3
4:17:48 2
4:28:17 1
4:37:09 Conclusion

UPDATED TIER LIST:
60. Bolin
59. Alleria
58. Mirage
57. Nivus
56. Cronan
55. Veruk
54. Kutsao
53. Jigou
52. Malik
51. Dierdre
50. Tramin
49. Karkinos
48. Razz and Rags
47. Prince Denas
46. Xin
45. Grawl
44. Thor
43. Bruce
42. Saitam
41. Lilith
40. Ingvar
39. Asra
38. Jun’pai
37. Margosa
36. King Denas
35. Grosh
34. Magnus
33. Oloch
32. Ashbite
31. Eridan
30. Arivan
29. Faustus
28. Bravebark
27. Mortemis
26. Jack
25. Dante
24. Sha’tra
23. Dianyun
22. Doom Tank
21. Kahz
20. Hacksaw
19. Blackthorne
18. Lynn
17. Gerald
16. Oni
15. Reg’son
14. Beresad
13. Ten’shi
12. Alric
11. Vez’nan
10. Catha
9. Elora
8. Phoenix
7. Ignus
6. Bruxa
5. Durax
4. Wilbur
3. Murglun
2. Bonehart
1. Eiskalt
1.Eiskalt