It depends on the context, but in general it is better to avoid that.
You can say, for your particular case:
- Merci pour votre aide précieuse: Thank you for your precious help
- Votre aide m’a été utile: You have been helpful
But utile can be used positively in French language:
- Bonjour, puis-je vous être utile?: Hello, can I help you?/do you need help?
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