Redmine

I never used redmine csv import feature but reading:
https://www.redmine.org/projects/redmine/wiki/HowTo_import_issues
I don't see why it wouldn't work.
Maybe you could detail what you mean by "the result wasn't good".

Yesterday I finished the import.
I managed it by doing some steps:
Converting the xml to csv using this online tool:
http://convertcsv.com/xml-to-csv.htm
This was the only one that could handle the size of my xml, aproximatly 11MB, for free.
Then I used H2 database to convert the csv into a table to treat the data more in a more efficient way using SQL. This process was necessary because every update made on codebase's tickets created a new collumn on the csv file and on redmine import I could select only one to be the "Description". So I joined all collunms and also treated some fields to make then match to what our redmine already have.
After exporting the table on H2 to CSV Was necessary to remove some accents that was creating problems during the importation with sed on shell.
Finally I could import the 1280 tickets sucessfully. Thanks!

Hi, nice.
That tool you mentioned is OK as it doesn't send the data to remote server and does all conversion in the browser.
But beware of using web tools as they could be used to harvest private data.