I personally feel that Gatka is for the 'martial' use of the Tulwar, in that, it not only demonstates the sword play but increases coordination, stamina and balance.
I do not agree that it is just dance movements, a number of Martial arts had to go 'undercover' because of restrictions imposed by the ruling elite (including colonial rule) Capoeira was originally disguised as a dance as it was outlawed, but do not be fooled by the 'strange' dance like movements which are used as avoidance and well as attack.
http://www.cwo.com/~lucumi/capoeira.html
With regards Gatka...I am not saying that swordsman entered the 'melee' like bionic windmills but techniques used would be effective. Especially, I feel, against 'regimented' cut and thrust techniques. I am not saying, either, that Gatka is the only way the Tulwar was used.
Many martial arts involve 'dance'....
Martial Arts
http://en.wikipedia.org/wiki/Martial_arts
"......As mentioned above, some martial arts in various cultures can be performed in dance-like settings for various reasons, such as for evoking ferocity in preparation for battle or showing off skill in a more stylized manner. Many such martial arts incorporate music, especially strong percussive rhythms.
Examples of such war dances include:
• Buza - From Russia.
• Panther Dance - Burmese Bando with swords (dha)
• Gymnopaidiai - ancient Sparta
• European Sword dance or Weapon dance of various kinds
• Haka - New Zealand
• Sabre Dance - depicted in Khachaturian's ballet Gayane
• Maasai moran (warrior age-set) dances
• Aduk-Aduk - Brunei
• Ayyalah - Qatar
• Khattak Dance - Afghanistan
• Brazil's Capoeira, as well as some similar Afro-Caribbean arts
• Dannsa Biodag - Scotland and Scottish sword dances
• Hula & Lua - from the traditions of indigenous Hawaiian
• Combat Hopak - From Ukraine
• Yolah - From Oman/UAE ......"
Regards David